To add an admin begin in Mission Control (you can also find this under your left navigation Settings tab and then Admins). Select Manage Admins from Mission Control.
Use the search bar to search for a member by name or email address. Once found then select their name.
If the individual does not already have an account then enter their name, email, and explanation for your invitation. Cause Machine will invite them to create an account.
Next select which community permissions they will have access to manage. Help text is provided on the page to explain what each permission allows.
Follow community permissions by site feature permissions.
Finish up adding an admin by selecting their Community Trend Report frequency and then send the invitation.
You can always come back and edit someone's permissions at a later date if needed.