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.
There are several style of clips but it will typically look like one of these.
This is an assortment set we sell, part # S109
If your needle allows for a clip, it will have an indent running around the top of the needle, similar to this one
Be aware that a sticking needle may also be due to a damaged viton tip. If the needle is pressed into the seat, as often happens while float adjustments are being made, a line will be indented around the needle which will result in sticking. If this is the cause of your sticking needle, replacement is the only option.
If your needle doesn’t show any signs of damage but is still sticking, use some mineral spirits and a clean rag to gently clean the viton tip. When you don’t see any black residue coming off the needle, it’s clean.
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.