1) Buy a badge at least 48 hours or so before the housing portal opens.
2) You get sent a time (eg. 1:20pm)
3) Housing portal opens. 2020 date is not yet released, but it was January 27th in 2019, so it will be about that time. Again, you need to have already purchased your badge before this.
4) Housing portal opens at 12noon Eastern, but (in my example above) you can't book until 1:20pm because that was the time you got.
5) Your time comes at 1:20 [still just the example here]. Have all your info credit card and name and email of those in your room ready. Search portal (number of people in your, maybe sort by distance to convention center) and book your room quickly. If you take too long, you may find that hotel you were working on get sold out as you were typing.
The rooms that go quickest will be the ones closest to the Convention Center. You probably won't have too much trouble getting on in the city. So, if you value low cost over proximity, you may fare better.
If you have, say, four people planned for you room, have all 4 buy a badge in advance so they each get a time sent to them. Then, have the best time book the room. If you just count on doing it yourself, you will only get 1 'lottery ticket' to the housing portal.
That's pretty much it. It does mean that you need to understand what you want (and, to a large extent, who is going) about 7 months before the convention.