Click on "contacts" on the left-hand side navigation
Click on the contact you want to edit
We're going to use Bob Fakename as an example.
Underneath Bob Fakename's picture on his profile, click "edit"
You'll be taken to this page where you can edit all of your contact's information:
Pay special attention to the "status" of your contact at the bottom of the page if you need to change their giving status.
Click "Save Contact" and you're done!