If you are a City Administrator, you can give other members of your City admin privileges. To do this, log in to your City and click on the "Configure" button in the upper right corner of the top navbar:
(If you don't see a Configure button, it means that you don't have admin privileges - make sure you logged in with the credentials associated with a City Admin.)
From the Configuration page, select Manage -> Users from the left menu:
This will open the User Management Page. From here, find the user you want to make an admin (either by scrolling through the list or by using the search in the right corner) and then set their role to cityAdmin:
The change becomes effectively immediately (no need to click "save"). If the user is already logged in, you can ask them to just refresh their page and they should see the "Configure" button appear in their top navbar, representing that they can now administer the City. If they aren't logged in, they will see the "Configure" button upon their visit.
Making a user a City Admin allows them access to all the features available through the Configuration page. However, it does not allow them to update the billing information for the City. Only the City Owner can update billing information. If you need to change the owner of a City, please enter a ticket through the blue help button in the lower right corner of any City page.
If you want to give a user access to restricted views and/or tools, but don't want to give them full access to all admin configuration features, you can do so by creating custom roles and making certain views and tools available only for users that are assigned a particular role. Please keep in mind that City Admins are able to edit and delete any view in the City and are able to access all of the data contained within a City. They are also able to make other users admins, as described here. Exercise caution when deciding who should have this level of access.
You can revoke a user's admin privileges at any time by following the same instructions above and simply unchecking the cityAdmin role for the user.