Classifieds- Where/how does someone purchase credits?

Hey there~
I have set up classifieds and have a question about purchasing an ad. I have logged in with a "test" user and have attempted to create an ad, when I click on create (once all of the fields have been populated), I get this message: (please see screenshot). The problem is, I cannot purchase them from this screen & I cannot purchase them from anywhere! Additionally, once it gets to this point, there is no way to save the listing. I have attempted to save as draft with no luck As admin, it works fine. As a Test user - not so.
Please help,