For some reason I can not figure out how to add stuff to a combo box. I am missing something, but not sure what.

I would like a drop down list of the diff states that the user would select and whatever they select needs to be used later. (set it = to a variable) So I made my little combo box, tried to add but am not calling something right. I know this is prob very basic and easy but I couldn't find it on the web already, since it is too easy. Thank you for your help.