1) jack the car up (or put it on ramps)
2) crawl under and find the old mount
3) undo the bolts that hold the mount in the bracket at both ends. sorry, i don't remember the size
4) pull out the old mount. it may be necessary to use a pry bar or something for this because there's not a LOT of room to play with. if necessary, you may find removing reomving the front bracket from the engine makes this easier
5) put everything back in in reverse order. i don't know the torque specs off hand, though. a focus repair manual would probably have them. be patient with everything bc it IS a tight fit! you also lose the play built into the original mount, so that makes it even more difficult (of course, that's why you're replacing the mount in the first place). it took some experimenting to figure out the order to put stuff back in, but i think i put the back end on first (the one that mounts to the x-member) and THEN i put in the end that mounts to the engine. probably doesn't matter though.
the job isn't that hard to understand once you get under there. it's just doing it that is the PITA!
just visiting now....