Navigate to the Locations > Community page > navigate to the "Users" tab and select the user from the list.​

Press (...) menu top right > select Edit.
​

Manage the "Administrator" switch. You can disable it, and the user will become a member, or you can enable it, so the member becomes an administrator.
​

If the "Administrator" switch is enabled, you can customize permissions.

Press Save to confirm the change.