Log into the VRChat site, go to downloads, and get the latest copy of the SDK. Check what version of Unity should be used and use it.

Assets > Import Package > Custom package...

VRM0 > Import the VRM

Assets > Import new asset... the FBX (maybe we don’t really need the fbx)

Select the FBX

Rig section: set Animation Type to Humanoid, Apply...

Configure... button under Avatar Definition: Head section, Jaw will most likely need set to none. Verify other bones are correct. Apply, Done.

Materials section: copy the VRM materials to the appropriate Remapped Materials slot if needed. Apply.

Stick the VRM in the scene.

VRM0 > Duplicate and Converter for VRChat

Combine Meshes checked

Swaying Objects: Convert VRM Spring Bones Only (don’t need coliders)

Select the outputted avatar, a few things to adjust in the VRC Avatar Descriptor: