The Hangar is where you stuff your available ships with equipment in order to complete missions with them. This is a very daunting Task at first, and will take a lot of practice.
Customization has been covered by the devs in the "How to play Ring Runner" video. Additionally, there is a detailed video here:
For any more info, check out the Stats Screen (By clicking the ? button in the bottom right while customizing a ship).
It will give information about node types, ability types, and more importantly, Pictures!