i got it off chocobo world, but whenever i use the command it says "mog isn't here".
what is mini mog supposed to do?
and how does one use it?
Although I've never had a PocketStation, and thus never actually gotten MiniMog, I do know this - MiniMog is a GF ability, not a GF himself. So, you need to find Mog's Amulet in Chocobo World and then use the item to teach one of your other GF's the MiniMog ability (like you'd use say, a J-Luck srcoll to teach a GF the Luck-J ability. The MiniMog ability then becomes a command ability, and when used in battle, Minimog is supposed to appear and perform a dance which heals all of your GFs.

Now, if you've done all this and it still isn't working, the only thing I can think of is that you may not have enough cash to get it to work, since calling MiniMog costs Gil. It generally costs your characters' average level times 100. So if your characters levels are high, it could possibly be too expensive for you, but who knows? Hope that helps somewhat.