In Island Builders version 1.4.1, conclude the Altador Cup tie-in event by engaging in a conversation with Ariel the Ruki. Once you’ve gone through all of Ariel’s dialogue related to the event, you will obtain a neomail containing the avatar as a reward (assuming your Neopets account is connected within the app). Please note that there might be a delay of several minutes or potentially more before the avatar is actually granted.