Right as alot of people seem to be a bit lost when it comes to fitting a lower strut brace I thought I would take a couple of pics of mine to help. Although to be honest if you jack your car up it is all very obvious where it goes.
Step by step:
1) Jack your car up on both sides and place axle stands underneath(They WILL save your life)
2) Pick up your strut brace and you will notice it lines up with two nuts under the car by the wheels. The nuts are the wisebone nuts, you need to remove the nuts on both sides. You DO NOT remove the bolt

Pics of where you need to fit the brace:
Drivers Side
Passanger Side
3) Then you just fit the brace onto the bolt ends, where you removed the nuts, so that when you put the nuts back on they are sitting in the cups of the brace. Also note that on OMP braces the sticker should be facing the rear of the car:
You will also find that it will be easier to put on if you fit it on the drivers side first.
Also note that the nuts can be very tough to get off, especially if you havn't got a lift. If you end up having trouble you can always cheat and do what I did and get a garage to do it, I just slipped them a fiver. It is a very quick and easy job as with the upper brace.
4) Once you have it in place just pop the nuts back on and tighten properly
Pictures of mine fitted:
You shouldn't have any clearance issues if you have not lowered the car, even speed bumps are fine. You just need to be careful if you go on really unlevel ground.
If anyone can add the size of the nuts that would be helpful I can remember if they were 19-20's?