Current team admins can give other regular users, members, admin privileges by going to the "Member" page under the corresponding team. This is an Admin functionality and hence is only accessible via Mesh AI's web application and not via iOS nor Android apps.
There, you will see "Manage Members" on the top left of the screen. In the member table, locate the row for the person, click edit (pen) under "Details" to open a window for "Edit Member Details".
You can click the admin option (click the box to the left of "is an administrator of the team") for the member and then click "Update Member Details". Voila!