You should give them admin access for the games page and also add them as contributer to make them appear in the game as team member.
To do so once you have created the page for the game, click on edit the page, in 'more' tab click on 'admins' add the team members itch user name and send the request url (it will popup) to him/her, once you have added the user name you will see a table above the text box with a checkbox for contributer check it and you are done.
Hope this helps you and anyone looking help in this section