You will need the picatinny mount which mounts the sight to your weaver base. The weaver base mounts to the gun's receiver, the picatinny mount mounts to the bottom of the sight with two #6-48 screws, the picatinny mount (attached to the sight) then clamps onto your weaver base.
Depending on which weaver brand base you buy, you may have to lightly file the slot sides you intend to place the picatinny mount in.