As Harbinger956 said, trading in this game, is by doing a deal with some other player for an agreed amount of FP's.
You agree on which GB each of you put the FP's. And also how many each side put.
For example, a trade of 100 FP. He will put it in my Arc, and I will put it in his Zeus.
This type of trades are best done within a guild as there is no FP police in the game if one cheat and put less FP's. So beware trading with a strangers.