VRC Avatar descriptor (Script)

Im trying to make an avatar, but the VRC Avatar Descriptor (Script) isnt showing up for the components. Ive looked up tutorials and still cant find out what the problem is.

You need to have the vrchat sdk installed on your unity project. You do that by installing and updating it through the VRChat Creator companion https://vcc.docs.vrchat.com/

Also make sure that in the VCC use you are using SDK 3 and selected Avatar not worlds