It does not matter which you choose for battery hot and which for ignition "ON", just so you know which is which and they are separate terminals. They are either all connected to each other or all disconnected to each other when switch is operated. So mark the switch yourself.
When wired, you will find that one is always hot no matter the key position and the other two will only be hot with key on. So those two become "ignition on/run" terminals. Kapish?

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn