When at https://play.alienworlds.io, select "Inventory" in the menu. Find the avatar you like and hover over it (desktop) or tap it (mobile) and then click "Set As Avatar" to select it. Confirm the WAX popup and that's it.
When at https://play.alienworlds.io, select "Inventory" in the menu. Find the avatar you like and hover over it (desktop) or tap it (mobile) and then click "Set As Avatar" to select it. Confirm the WAX popup and that's it.