Some but not all carburetor kits include a clip that attaches the float to the needle. This is so the needle doesn’t stick in the seat, which can happen with the lousy gas we now have.
Hook the rounded end to the needle and the other end simply hangs onto the float. Just make sure that when the float moves up and down that it pulls the needle out straight and not to one side where it will bind.
Watch a video about how to connect the clip: