This story shows how to install a lockset.
If you are replacing a dead bolt or handle, simply insert the new parts into the existing holes (steps 6 and 7). Before installing check that the new dead bolt will fit in the hole and that the existing mortises for the latch and the strike are not too large. (It's easy to enlarge a mortise, but it's difficult to fill in a too-large mortise so it is not noticeable.) You may need to buy a separate, larger strike plate.
If you buy a unit with a security box and strike plate, you may need to widen and deepen the strike hole, and perhaps enlarge the strike's mortise as well.
The door frame should be in good shape. If the dead bolt slides into the jamb only, an intruder will be able to kick the door in. A bolt that slides into the stud will be much more secure.
1 or 2 hours to install a new lockset or dead bolt
Drill, hole saw and spade bit of the correct sizes, hammer, chisel, screwdriver, awl
Accurate measuring and drilling
Place a drop cloth on the floor under the door.
Lockset or dead bolt with accompanying hardware
Determine the best height for the lock. The lock comes with a paper template. Fold the template and tape it to the door. Select a 2-3/8-inch or 2-3/4-inch backset. Use an awl or sharp nail to poke a small hole at the center of the cylinder hole on the face of the door and the latch hole on the edge of the door.
Insert the inside portion of the lockset -- the one that has a tab that fits through the latch -- until it rests flush against the door. Insert the other portion and drive screws to attach the two. This can sometimes be tricky; have a helper hold the inside portion while you drive the screws.