Ship building is easyer this time around, you have an interface that shows power sources as blue, conduits as yellow and powered/unpowered modules as green/red.
To power a module you must drag a power conduit from a reactor to said module, keep in mind that everything has an input point that you must connect to, its rather obvious.
Also conduits behave rather strange, click only once to place a 4 junction, hold click and drag to place a continuous line.
Place a command point and link guns and such by placing a node, numbered square, near said module and another near command point.
Your character can only walk in rooms, rotate stuff with Q, add support structures if your ship falls appart, add more reactors if needed, etc.
Just follow the interface and you should be fine, theres a button center top for it.