omegaredmedia on "How do you make checkbox create automatic tag?"

I am looking to have a checkbox on my form create an automatic tag to my custom post type. At the very bottom of my form I have a checkbox to make my listing featured I want it to create an automatic tag for that listing (EX: Featured Roping or Featured Clinic)

http://teamroper.com/submit-an-event/

I feel like this should be simple but Ive hit a mental block any help would be awesome