Remove the display assembly from the iPhone.

You may have to reuse the earpiece grille and the clear plastic ring around the front facing camera from the old/damaged assembly. This will depend on where you buy the replacement part.

Your replacement display may come with colored plastic film on the back of the LCD. If so, use the pull tab near the home button to peel the plastic film from the LCD before installing the new display in your iPhone.

After reassembly, note the following:

Clean the touchscreen surface with an alcohol wipe prior to turning the iPhone back on. The alcohol helps dissipate any lingering static electricity, which can cause problems with the display.