Shut valve won't turn back on

I had a leaky toilet, turned the water off at the wall. Replaced the rubber stopper in the tank. Went to turn the water back on.......no water. Have I broken the valve by turning it off? What now?

If it was old and a multi-turn valve, the washer may have basically come apart clogging the lines when you opened it back up. Usually easier to just replace it, but wait for some other ideas.

Repair?

How would I go about replacing this? Any ideas?

You have to turn off the main water shutoff to work on a stop valve. Once the water is turned off, take a crescent wrench and unscrew the nut closest to you and pull out the stem. There should be a rubber washer at the bottom of that stem. If it is missing or damaged, bring it to a ma and pa hardware store and have them replace it.

It's also possible that some debris has clogged your fill valve. If the stop valve is fine, then you'll need to replace the fill valve.