With the car off, push in the Schrader valve on the fuel lines with a rag to let off the fuel pressure (collect fuel in rag to keep from going all over your engine bay). Then unbolt the fuel rails (and remove anything that might be in the way) and gently pry it off the manifold. You may have some injectors that come with the rail, and others that stay in the intake. Just make sure you get all the old "O" rings out before you intall the new injectors. Then make sure the new injectors seat properly in the fuel rails and intake before you tighten it back down. Some say you should lube the new "O" rings before install to make it easier. Install any other parts you May have taken off. Once done under the hood, cycle the key to the on position, and leave for a couple of seconds and turn off; but don't start the car. Your priming the fuel pump to put pressure in the lines. You should do this maybe 2-3 times if that. Check the lines under the hood for any leaks.
If none, start her up!
NOTE: If you're going with different injectors than what you currently have installed, you will need to have your MAF calibrated for the new injector size.
2000 Mustang GT-Former giggle gas addict
1990 Mustang GT w/ Vortech V3
***resident gun idiot***