Replacing the ignition switch

Hey! We bought a 1980 Bronco a few months ago. We knew it was going to need a little work, but it's turning out to be a lot more than I bargained for. The guy I bought it from said he had recently replaced the starter solenoid. Then we got it and the battery kept dying. We tested the alternator at O'Reillys and they said it was bad. So we replaced that. Battery kept dying so I took it to a mechanic. They said the guy that replaced the starter solenoid had the wiring all kinds of jacked up, they fixed that. Then the battery died after about a month so we replaced that. It ran great for a month and now this battery keeps dying. We jumped it the other day and after I connected the cable the truck began trying to start on it's own. Without anyone turning the key. A little research resulted in us thinking it's the ignition switch. But I can't for the life of me figure out how to change that out. Anybody know how to replace that?