I would think you need to :
1) Have your incoming cable or satellite signal split to feed each showstopper and optionally the TV directly for watching live tv (although I never do anymore)
2) Take the S-Video and audio or the RCA video/audio jacks from each showstoper and plug into the inputs on your TV.
3) If it an older one that only has one input - a Coax jack, then I would say you need either:
A) An audio/video switch to toggle the inputs to the TV - this might be a 2-way switch for the two SS's or a three way - two SS's and the original cable input
B) A modulation solution that would take the cable input plus the outputs from the two SS's and combine them to one coax line to the TV. ChannelPlus for example has a nice box - the 3025 I think - that takes the cable plus two inputs, modulates the two inputs to occupy two unused channels and then can send out up to 5 coax runs to 5 devices. In this case the TV would have one incoming coax and each showstopper would be a channel. Then you have to deal with the remote control aspects. The Channel+ box has an IR engine so with IR targets + emitters it can take care of it. Scan the forums for IR or IR emitter and see what you get - this has been discussed a lot.