The Specifics:

Standard Options/Controls

Colors:

To change Aurora colors you can change the colors set here. Either in the Material Tab, or The Shader Tab. The Shader Tab view is Labeled for easy use.

[Texture] Patterns:

The 'Streaks' Value changes the number of Vertical Streaks that go across the entire Aroura. Default is 4. Try playing around with it for busy or sparse streak effects.

Editing/Moving The Curve:

Any basic movements like moving the start of the Aurora around in the scene should be done by grabbing the 'Borealis Root' Empty. WARNING: Never Rotate this Root. Do rotation in edit mode on the curve.

This Empty can also be used to Resize the entire Aurora.

Note: When the Aurora is resized using the Root you may need to tweak more settings afterward.

There is another Empty called 'Height Controller' just above the Root Empty, you can use that to make the Aurora taller or shorter by moving it up/down. Note that taller values can cause issues. Use with care. Don't rotate that Empty either.

To Change the Shape of the curve that generates the effect, Select the 'Major Curve', or the curve directly beneath the Aurora, and go into edit mode. 

WARNING. The X axis will translate with an offset, so move the curve carefully when moving on the X Axis in Edit Mode!

Multiple Auroras: For most cases you can add another aroura by clicking on the Major Curve and going into edit mode and duplicate that curve while in edit mode. But lets say you want two with different colors or Geo-settings. Then you'll have to Append a new one into your scene. 

[Geo-Nodes Settings]

Here is the Geo-Nodes settings, there are quite a few, but don't worry they are all easy to explain.

Resample Length: This setting changes the Smoothness of the curve based on Length of the Curve. Basically keep this value low if you want a smooth curve. Turn this value up if you want sharper curves.

Note: Resample & Frequency go hand-to-foot. If you up the Frequency, Lower the Resample

Aurora Frequency: Sets the Frequency of the Aurora. Higher values make the curve more frequent. More waves vs Less Waves

Aurora Procedural: This is the Value that you can animate to make the Aurora wave. By default it has a Time-Driver on it, you can remove that driver if you want to manually animate, or change the driver value by clicking the purple field.

Frequency Amplitude: This is a Vector Value, so it's actually Three Values. X.Y.Z. These values determine how much the system multiplies the curve. Mostly you'll only use the top value 'X' '3.3'. But you can also use the bottom value 'Z'. The 'Y' value has no real application.

Z Noise Switch: This one is simple. The standard Aurora Effect actually does curve up and down randomly ever so slightly. You can change this to a value of 0 - 1 to turn off that random up and downward curve if you don't need it and want the Aurora to be flat on the Z Axis. 

Note: The Z Noise Switch can also fix some rotation errors when you have complex or wrapping curves. 

More Advanced Options/Controls

Material Blend Mode:

While the Aurora is selected, you can go to the material tab and change its Blend setting.

Use Alpha Hashed when you do final renders, or need/want Reflections or Compositing Data.

Use Alpha Blend for testing or super quick renders.

Advanced Colors:

These Factor Ramps, Found to the left of the color settings, control the transition between the colors. You can drag the points around to get different gradients between your three selected colors.

The top Ramp changes the Top - Middle transition

The bottom Ramp changes the Bottom - Top Factor

Some Extras

These settings in the Shader Graph can give you greater control over some more advanced settings like Emission and left-right Mix.

Even Mixer: The shader is nice and even because of this setting. But if you want the Aurora's 'streaks' to fade away near the end of the effect, change this setting. Not super useful, but worth pointing out.

Emission Value: The Emission Value (Default 4) is the overall Emissive brightness of the Aurora.

Transparency Mix: This node mixes the effect with a standard Transparent Shader, useful to make the effect more see-through, or to fade out or in with animation.

Animate: In the far left of the Shader Graph there is an 'Animate' Labeled Node. You can either manually edit this for animating the movement of the texture, or use a driver. You can change the current Drivers speed by left clicking the purple field. This effect is not always super impactful.

Rendering Settings:

These are some FAQ tips on Rendering

Cycles & Eevee

Blend Mode: Make sure Blend mode is set to 'Alpha Hashed'. Otherwise you wont have any Reflections NOR Layer Data like 'emissive'. If you don't want reflections or data, use 'Alpha Blend' for faster renders. Alpha Hashed is on by default.

Note: Blend Mode 'Alpha Hashed' looks poor in the viewport, but can easily be denoised in final renders in Cycles and Eevee.

Light Bounces: When using Cycles sometimes the effect might look black when you have a lot of them in a row, or you're looking straight along its path. To fix this simply up the number of Transparency bounces in your Render settings.

Importing:

When you want to add this to an already created Scene you MUST make sure you use 'Append'. You can find Append under File in the blender top-bar.

Once you hit Append, find the Aurora File wherever you saved it. Then click 'Collection'>'Easy Burn Aurora'. Then click 'Append'