Rotate the soldered lens in its clamp until the area that you want to be the top of the lens is up. A lens as heavy as mine seemed to call for a sturdier finding than a mere jump ring, so I pulled one of the metal handles off of a small binder clip to use for each of my necklaces. Any other found items will work with solder, as long as their melting point is higher than the melting point of solder.
To attach a jump ring or other finding to the soldered lens, first melt a lump of solder onto the spot where you want the finding to rest. Then, holding the finding with a clamp in your non-dominant hand, rest it on top of that mound of solder, and use the soldering iron in your dominant hand to re-melt the lump. As the lump melts, push the finding into it so that the solder will harden around it, and use your soldering iron to smooth out any imperfections.