If you mean making the Tournament Post such as this, hosting it, keeping score, etc, then you need to make a request to do so on the next scheduled tournament's answer post.
If you have an idea for a tourney you would like people to participate in, you may post it on that thread in the second link, however it may not be used until a long time because the only the post with the most upvotes will be chosen for the next tourney, and there are many suggestions already there, unless you happen to get a lot of upvotes.
The next supposed Tournament after the current Scrabble Tourney will be Pimplup's Same Team Tournament.
Hosting Policy is here.
