Well, I think the idea of "freewriting" is that you ignore typos and just keep throwing words at the screen. So the textbook answer is probably to ignore your typos.
But in the long run, the question is surely, "What works for you?"
When someone with more experience gives me advice about how to do a job, I generally try their advice at least once -- whether that job is writing, auto mechanics, cooking, etc. Even if it doesn't sound like a good idea, maybe if I try it, I will see why, in fact, it IS a good idea. But once I've gained some experience myself, I usually find that there are many times when the textbook approach is a waste of time and I can take short cuts. Sometimes things that work for other people don't work for me. Etc.
So I'd say: Try the textbook approach, that is, don't fix your typos, just push ahead. When you feel like you've given this technique a fair try, then decide for yourself whether fixing your typos as you go is productive or not.
Personally, I wouldn't say that I use "freewriting" per se, but I do routinely just type in every idea that comes into my head, throwing text at the screen as fast as I can, and then later go back and clean it up and re-arrange it into a more logical sequence and delete stuff that I now realize is superfluous, etc. If I notice a spelling or grammar error, I'll back up and fix it. But I don't look for such errors. I think if I really got a row off on the keyboard or some such so that everything I was typing was gibberish, I'd back up and fix it immediately, while I still remembered what it was I was trying to type.