Procedure:

Remove wheel

Get on the lock nut of the tie rod end, and turn it clockwise 1 turn. It will be difficult to start, but once free, will turn easily. This will back it off from the tie rod end.

Remove the tie rod end from the wheel knuckle. I can't remember if there's a cotter pin holding the nut on or not on the Focus. If there is, remove it before undoing the nut. It's self explanatory.

unscrew the tie rod end from the tie rod. Count the number of turns it took to remove it, and write that number down. This is important, and could save you from needing an alignment after replacing the tie rod end.

Screw the new tie rod end on the same number of turns you used to take the old one off.

Cinch the lock-nut back against the tie rod end and make sure it's snug.

Drive the tie rod end back through the steering knuckle, and tighten the nut holding it on. Replace the cotter pin if one was provided.

Replace the wheel and tighten the lug nuts to specification. Using a torque wrench (optional) is a good idea.