There are two ways to create managed leagues.
Option 1: Manual Invites
Manually creating leagues and inviting
The first way is to manually create leagues, and invite users to those leagues. This is useful if you have a specific number of leagues in mind that you would like to set up.
Option 2: Draft Queues (automatic)
Set up draft queues and giving your followers a landing page to queue up for draft times
The second way is to set up an invite landing page and let people choose times to queue up, via draft queues
If you are expecting a lot of sign-ups and don't want to limit the number of leagues that are signed up, then setting up times for people to queue up for drafts is the best way to go.
There are no limits on how many leagues can be formed for each draft queue. For example, if 1,005 people queue up for 10-team leagues at 7:30 pm tomorrow, 100 leagues will be formed, and 5 people will be left out to try and queue up again.