Installation

In Blender open Edit, Preferences, Get Extensions, then use Install from Disk and pick the zip.

Create a character

1. Open the sidebar (N) in the 3D Viewport and click the Character tab.
2. Pick a preset picture, or click Surprise Me.
3. Use the tabs (Body, Face, Skin, Hair, Outfit, Animate, Rig) to change anything. The character rebuilds live.

Animate

1. Select the character and open the Animate tab.
2. Click a clip to add it as a layer, or a face pose to set the face.
3. Use the Rig tab to switch IK/FK, snap, and pose with the controls.

Export to a game engine

Click Bake in the Rig tab: the animation is baked to the Mixamo deform bones. Export the armature and meshes as FBX or glTF.