Step 1: What you'll need
the black droid gun that comes with almost every lego star wars set (top left)
the smaller peice next to it, which we will call the right angle piece
the 1x1 piece with the tube on the top
the + shaped piece with a lego stud on the top (bottom left)
the circular piece that slips over the + shaped thing
and finally, the slimmer version of the above mentioned piece.
Step 2: Putting the pieces together
also, take a look at the second picture and put together the + shaped piece, and the two pieces that go over it, just like i did.