hello, thanks for trying out "Stargrid".
1) open up the inventory here
2) craft blocks from resources and place them in the hotbar, the red zone at left bottom.
3) close the inventory and the blocks you put into your hotbar in step 2 appear on the bottom left
4) click one of those blocks, try hull for example and click it adjacent to the blocks on your ship.
5) the hull block is now attached to the ship.
6) as for weapons like a machinegun, place a "hardpoint" block
7) place a weapon like the "machinegun", on top of the "hardpoint"
That should be it! :)
if you accidently removed your ship you can spawn it again with a button on the bottom right:
click the spaceship icon and click somewhere in the green zone in the world, it'll place the core of your ship which you can build around.
Have fun!