Pick an avatar, calibrate it and enable any extra features that you may want.
You can find all the avatars available to you in the LIV overlay's Avatar tab, as well as a bunch of toggle options. Select your avatar.
The next step is to calibrate your avatar.
1. Click on Calibrate T-pose and follow the instructions.
2. Click OK when prompted to save. If your calibration doesn't turn out well with the
T-pose, click on Edit calibration right below and try out manual calibration.