1) Type /mac config
2) Select the bar you wish to act as posses bar
3) Right click it, check "possess", click "done"
4) Left click your selected bar until it says something like "bar 1 - possession"
5) Type /mac add 12
6) Type /mac config
7) Type /mac bind
8) Setup your keybindings
9) Type /mac bind

Done :-)