[Suicide Junkie]

Hi Mac.

The first one there:
You can click "add new type" when you're selecting a design type. The type names are arbitrary and have no effect on the game other than to sort your designs into handy categories when building and designing.
I have improved the default types in the latest version, though.

The rest, ZA's got it.
You have to choose a weapon mount. The guns range from 20mm to 100mm, with accuracy bonuses on the small guns, and range bonuses on the big guns.
The 20mm mount guns will cost only 1-3kt of space, so there will be plenty of room for them.