https://github.com/Assistant/ModAssistant

Download the newest installer from the release section and run it. This application auto-updates when launched, there is no need to download a new release each time.

• Run the game at least once before trying to mod the game! This applies to reinstalling your game too. All mods are moved into an Old X.X.X Plugins folder on first launch to avoid version mismatches, so make sure to do this before installing mods on a fresh version.
  
• Once that's done, simply check off the mods that you wish to install and click the Install or Update button. Likewise, click the Uninstall button to remove any mods.
  
• Mods are installed to IPA/Pending until the game is run. Boot the game to complete mod installation.

If you encounter crashing upon launching Beat Saber, after utilizing Mod Assistant, you can attempt the following.

• Reboot Computer (May not be necessary)
  
• Run ModAssistant as administrator.
  
• Uninstall BSIPA (in ModAssistant settings)
  
• Ideally uninstall all mods as well
  
• Verify Game files integrity for Beat Saber in Steam
  
• Launch Game
  
• Close Game
  
• Install Mods in ModAssistant
  
• Launch Game
  

Note: I do not claim responsibility for any issues you encounter with your game, or files. Do at your own risk. I am also not the creator of ModAssistant, and as such am not offering technical support for it.