If you want to play as St Louis City SC and actually participate in the expansion draft etc before the season, you have to jump through a bunch of hoops since SI develops very little between each years games and rarely anything for MLS. Which is a shame because this is one of the few times left that the MLS will have expansion teams added with drafts to create a team from scratch.
In 2022, St Louis SC is in the "Lower Leagues" (not loaded) instead of the MLS, even after the MLS season ends.
You'll need to create a new game with the below settings:
Select Team - Make sure you choose St Louis as your team before you create the new game, you can only select a team if you have no custom editor files. You can't join teams in leagues that aren't loaded if you use ANY editor files when you start a new game. You also cannot move your manager there using the in-game editor.
Start Date - You want to choose a start date that is before December (waiver/expansion drafts), I used the England First Champions League as the starting date, I believe it is September 5th.
Then you can participate in:
Waiver Draft - Dec 12
Expansion Draft - Dec 13
Super Draft - Jan 12