I need to know how to change the timing belt on.

You start by knowing the engine size and other important details like did the belt break while the engine was running, did it just slip while you were doing a maintenance replacement, or is the engine still running. Timing belts are never a job to attempt without having the service manual in front of you, otherwise you'll be back here asking a followup question every few minutes and wasting time waiting for answers. Haynes and Chilton books will get you through it, but nothing beats the manufacturer's manuals. AllData and Mitchell On Demand are okay too. I'd copy and paste the procedure if I could but I have never been able to access the sites.

If the belt broke while driving, the valves will be bent. Around the late '80s and early '90s Honda recommended replacing the belt at 75,000 miles, ... And they commonly broke at 65,000 miles.

If you have a cylinder leakage tester and compressed air, you can turn the crankshaft so no piston is at top dead center, then turn the camshaft so the valves for a specific cylinder are closed, then see how much leakage there is in that cylinder. You might be able to borrow or rent that tester from an auto parts store. The only other way is to install the new belt, then perform a compression test before you put all the covers and brackets back together.

If it didn't crank why are you assuming there's something wrong with the timing belt? I'd look for a bad battery or bad electrical connections first, especially given the age of the car. Rule out the easy stuff, then look at the less likely stuff.

Ahh. That makes sense.

If the belt broke while they were trying to start the engine, there is a slight chance the camshaft was in a position to have no valves fully open, so it's possible they aren't bent. What I would do is prepare the owner with a worst case estimate that involves removing the cylinder head to have the bent valves replaced by an engine machine shop. Very few do-it-yourselfers and few repair shops have the special tools needed to do that part of the repair.

Once you get the okay to do the work, turn the crankshaft only by hand, not with the car's starter, until it's at top dead center, then back it up about five or six teeth on the sprocket. That will insure no piston is all the way up. Now you can safely turn the camshaft by hand. Bring it to top dead center according to the timing mark, then you can bring the crankshaft back to TDC. Put the timing belt on, then rotate the crankshaft two complete revolutions by hand in the normal direction, and stop at TDC, then double-check the timing marks. If they're correct, you can do a compression test. The actual values aren't important at this time because to be accurate the engine should be warm. All you're looking for is do you have reasonably good compression in all the cylinders or are any real low.

If you have compression the engine can be run that way with the covers removed. I like to see it run before I take the time to put everything back together in case I made a mistake. This gives you a chance to see if the belt is tracking off-center on any pulley or sprocket which would lead to another failure.

If you get lucky and don't have to replace any valves, you get to surprise the owner with a bill much lower than expected. Who doesn't like that?