I bought the newbie pack that should have the avatar change item. But whenever I click the icon below..

You need to find an image to upload which the game is trying to do by accessing your devices gallery or camera functions. Assuming you are playing on a standard phone or tablet with these options then you may find that you don't have access enabled for the app to read your storage or access the camera. If its not asking you for access then you may have denied it access in the past and need to manually enable it in your devices settings.

If this doesn't help then there may be a compatibility issue or some other problem with the game on your device. You can report this to the game support so they can look into why its happening. Check the support page for details on contacting them.