I want to be able to clear out some of the junk in my backpack to make space for some more junk :P is it possible to do this from the main menu or can it only be done in game?
The backpack is not currently accessable from the main home base menu. You need to either start a mission or head to your storm shield and handle the contents there. The developers did say they they have this in their Todo list though. We should be able to access the backpack from the main menu in the future.