Interact with target is a keybind you'll find it in interface->keybinds. just use watever key
I suggest you make the following maccro(s) :
/follow main
/target focustarget
/focus main
use one key on your slaves to bind, all of them, the same above maccros. then, when your main choose a target, you hit that maccro. all will have the same target, as your main. then u hit the keybind "interact with target"
for spells use something like /cast [target=focustarget] Spellname;
Forgot to mention how to set up jamba :
-main has full party (slaves) names. in the party tab.
-slaves has only master name in the party tab.
slave needs to set the main name as "master". you need to do this manually on all slaves. to verify this is done/working, try sending an invinte to your slaves from the main. they should all accept automatically.