I know I'm probably blind, but I can't see how to do it. I know there isn't any combat yet, but so far the only way I can see to get the hull up to peak after you install a new hull module is to level up the base. Maybe that's intentional, but I can't imagine that will be intentional after combat starts. So can someone please point out to me what I'm missing? Thanks!

pull up the base window
then on the stats tab, next to the hull (if the hull is not at max) there will be a repair button and the cost