Should I take the nail out before you use fix a flat?

Yes, remove the nail. Fix-a-flat may work for a temporary fix but get a proper plug patch installed at your earliest opportunity. Take a crayon and draw an arrow on the sidewall showing where the nail was and you will be able to tell the guy at the tire repair where to look. The fix-a-flat also works better if the hole is on the bottom when you squirt it in.