FCB Midi out>Boss Midi In
Boss Midi Thru>JMP Midi In
Then run your audio lines with the boss in the loop of the JMP and that should do it.
Your boss may not have a midi thru (I don't know for sure) but if it doesn't there should be a setting that allows it to route the signals for the JMP to the midi out...in which case you'd apply that setting and use the midi out to run to the midi in of the JMP.
Download the manual for the FCB controller from behringer and read it cover to cover. It walks you thru things pretty smoothly, but it can be daunting for midi neophytes.
Someone please correct me if I've steered him wrong...this is why I gave up on the midi thing. I had it working but I felt trapped by my settings. Good choice on the FCB though, same one I used and it did a good job, although you can't toggle effects with it, but you could set the
expression pedals to transmit control change messages to link to the effects you wanted to control within a patch for the boss unit. Clear as Mud?