Find the timing pointer. This can be an issue as sometimes they go missing.
Clean the damper so you can read the numbers. Often a little paint on the numbers and wipe it off to leave paint only in the indentions works great. Make sure you know which side is BTDC and ATDC, you only care about BTDC.
So now you have a pointer, and readable markings on the damper.
Hook up the timing light to #1 cylinder. Front spark plug on the passenger side.
Unplug the hose(s) from the vacuum advance on the distributor, mark as needed, plug the hoses.
Find a wrench or socket, whatever it takes to access the distributer hold down bolt, make sure you can loosen it.
Should have asked this up front. Why are you setting the timing? Is this a new engine build? Or replacment engine? Just some new parts on an existing engine? Or just doing a tune up and want to check?
Start the engine, warm it up, get it off fast idle. You need the idle down near stock specs so you are not fighting against centrifical advance. Depending on what you are up against this may require a little idle mixture tuning, or even a carb rebuild if that is really the issue. Maybe a little blind adjustment of the distributor. Use the strobing light, watch the pointer and the timing marks. Rotate the distributor until the pointer lines up with the desired timing. If you have the fancy timing light with built in advance knob/buttons. That is a little different. You set the advance you want in the timing light and adjust until the 0° mark lines up with the pointer.
A possible issues are using an old damper that the hub has slipped. Or the fact the small block Fords were built with 3 different locations of the timing pointer. You have to have the right damper to match the pointer for the pair to work. Get the wrong mix of parts, the pointer and marks will not match and you can't set it (other than by ear/feel).