I may have just missed this option somewhere, but I can't find out how to put an add-on into a marketplace category.

For example, I've recently built a newer version of an ecommerce gateway, for SecurePay. It can easily be found if you search for it in the marketplace (and the one by jaredquinn also appears), but if I check the category checkbox for 'eCommerce', my add on is no longer listed.

I looked all through the options in the edit screens for when you are editing an Add-On, but the only thing I could see that was close was a keywords field.

So how to you put your add-ons into those right hand side categories?