Cap'n Trips

This is one of my desert island mods, along with Kerbal Engineer. I almost don't want to play without it.

Forgive me if this has been answered somewhere else, but I couldn't find a readme or anything that covered this. How do you decide what goes into the cargo compartments? The context menu only gives me an Enable/Disable Warehouse option. It defaults to carrying supplies and I can't seem to find a way to change it. This is in 1.1.