How do you reset the check engine light on a 1995 Toyota Corolla OBD1?

You can reset it by unhooking the battery for 5 minutes. it will just come back on if you do not repair the problem that caused it to come on in the first place.

Will it come on immediatly? Or will it take a bit of driving?

It may come on very quickly or may take a few driving cycles, hard to say. If it comes back on then there is a problem with the emissions controls.