Sorry to be late seeing this thread. Hopefully the good advice already posted by others has already helped you get everything set up. Let me just expand a bit in case others come across this thread in the future.
In the Premiere system that you have described, you have two components that are capable of movie playback. Those are the M500 and the M700. (For those who are perhaps not familiar, an M700 is a disc vault
with an integrated M-class player). In some installations, people have an M700, but they are not actually using the player capability. They're just using it to manage their optical discs. In other installations, they may be using the M700's integral player for one of their viewing zones.
So, how you proceed will depend on how your system is set up. The easiest thing to do is to look at the back of your M500 and your M700. Which ones have HDMI cables connected? Is it just the M500? Or does the M700 have one as well?
If you are only using one of the two M-class components as a player, that's the one you'll pair with the Strato using the Co-Star switch. If you are using both M-class players, you need to decide which of those two will be paired with the Strato. Your other player will remain un-paired, and you can continue to use it to play movies and music stored on the Premiere system.
As much as it generally pains me to watch myself on video, you may find this demo we put together prior to the Co-Star release helpful. A few small details have changed, but generally it's still accurate.
https://www.youtube.com/watch?v=mPi66M_OfEA