It is really easy if you have a key. (Most people want to replace the switch because they've lost the key.) Sometimes it's hard to see the pin thru the hole. Be sure whatever you use to depress the pin is about the same diameter as the pin itself. Too thick & you'll never get it depressed.
Another thing. Some of the older ignition switches require another step before trying to depress the pin. If you have a small nut (5mm) on the center back of the switch, first you have to loosen that nut. That nut should be soldered in place, so first you have to clear the solder (Murphy's Law states 'In order to do something, first you have to do something else') Once you have the nut free of solder, loosen it until just before it comes off the stud.(Notice that the cylinder has started to back out of the body.) Now you should be able to clearly see the pin thru the access hole in the side.
If you don't have a key PM me & I'll give you another hint.
Frank