Pass Variable To Marketpress Categories

I apologize in advance if this is slightly out of scope, but recently I've been using Gravity Forms to pass data to the various custom fields of MarketPress (i.e. I'm able to pass product names, images, files, etc. with ease) - however one of the sticking points I'm dealing with is setting the product category with Gravity Forms since the category field doesn't seem to have a DB variable I can pass data to.

Normally I'd try figuring this out myself however as I'm not too familiar with the MP architecture - I wanted to pretty much ask how I can format my data so that when Marketpress parses the form information - it will check off the categories the user specifies in the form.

Thanks very much in advance for any insights,

Charles