How to add Sparkles Geometry Node to your Object.

Select Your Object > Navigate to Modifier Properties > Add Modifier > Select Geometry Nodes

How to Change Sparkles Material.

Select your Object > Go to Modifier Properties > Sparkles_Material

How to customize Sparkles Material.

Select Sparkles_Colors capsule or Select Sparkles_Colors Layer in Outliner > Navigate to Material Properties, Sparkles_Colors contains entire Sparkles Material. From there, you can easily customize any Material.