Requirements
Quest with Virtual Desktop or PC vr.
Beat Saber on Steam set to Legacy build.
Mod Assistant (To install mods)
Open up Steam on your PC and go to your Library, click on Beat Saber > Manage > Properties > Betas > legacy. Install then launch the game and close it.
Next download Mod Assistant and launch hit “I Agree” > Options > Install Folder (It’ll be in your SteamLibrary folder example: E:\SteamLibrary\steamapps\common\Beat Saber ) if you’re having trouble finding it go back to your Steam Library Beatsaber > Manage > Manage > Browse local files then copy the file path.
Now click the Mods tab in Mod Assistant n’ scroll down to the Cosmetic section and look for Custom Avatars checkmark it and hit Install or Update.
That’ll create a CustomAvatars folder within your Beatsaber files, locate it and drop the .avatar file provided within. Then you should be good to go. ^-^