How do you teach already-potty trained dogs to (temporarily) go indoors on a pee pad?

I lost my dog recently, but this is just a curious question (maybe for a future dog!). When you have a dog that is already potty-trained to go outside, how do you then get them to go on a pee pad indoors, if/when there is, say, a blizzard outside – or some other reason why you can't take them outside, temporarily? I would imagine that would be confusing for them. Then afterwards, getting them to go BACK outside after the need for a pee pad is over?