Tap on "Edit Settings" in the upper right corner of your group. Here you'll find a list of permissions. If you are the group admin, you can adjust these permissions. The permissions are:
Withdraw - Can other users withdraw out of the account?
View Transactions - Can other users view transactions?
Invite Others - Can other users invite others into the account?
Spending Cap - What is the maximum amount that can be spent out of the account each day?