Documentation files are include in the package and you can find  some guideline on how it works here.

Installation

Go to the top menu

• Under "Edit" select "Preferences".
• Select the "Add-ons" tab on the left side of the Blender Preferences window 
• then select "Install..." at the top of the window and choose bumarin.zip. 
• A tab section named "Sculpting: Bumarin" appears 
• To enable the addon check the checkbox. 
• Save preferences at the bottom of window.

The file name must be bumarin.zip. If you have different copy of bumarin in the same directory (ex:bumarin(1).zip, bumarin(2).zip etc...) select the one you want to install and rename it bumarin.zip

Go to the top menu

• Under "Edit" select "Preferences".
• Select the "Keymap" tab and check if the top list is set to Blender. If the list is set to Blender 27X or Industry Compatible set it to Blender
• Save preferences at the bottom of window.
• Close Blender Preferences windows
• Go to View3D>Tools> Bumarin and Launch Bumarin
  
  

Go to the top menu

• Under "Edit" select "Preferences".
• Select Interface tab.
• Check Developer Extras
• Then go to the Experimental Tab and check Undo Legacy
• Save your preferences.

The last step concerns the UNDO task [CTRL+Z] which is in development state in Blender 2.9.

Notes:

Sometimes if you are a Windows OS user, before launching Bumarin you must clean your scene. It means that you must have zero object in your scene except objects generated by Bumarin.

When you launch Bumarin your environment switches to Right Click select mode.

Claypencil

Tubepencil

Revpencil

Dynaclay

Dynaclay with hole

Dynatube

Sonic Bum simple stroke

Build a chain with Sonic Bum

Leeloo

Leeloo clay extrusion

Sonic clay to build a pattern for Sonic Bum

Pattern is loaded in the Sonic Bum panel.
Draw your stroke and play with Live voxel.

Sonic clay with Live voxel

Add external object to Bumarin