After you have completed your work on the caliper, such as removing the old pads, and cleaning them up, they can be re-installed. Or, if you have new calipers, this is the time to install them.

Before installing the caliper bolts be sure to apply some thread locker to them. Use the blue thread locker than can be removed with hand tools, not the red thread locker as that needs heat to remove.

Hold the caliper up on the rotor and line the holes in the caliper up with the bolt holes in the steering knuckle. Get the first bolt started by hand.

Then, start the second bolt by hand as well. Doing so helps ensure they do not become cross-threaded.