Upon creation of the league, the commissioner must join that league themselves. Then the commissioner can click on the ‘Invite’ link and invite other league members. You can invite members either by sending them the shareable link, or entering their email addresses and hitting the ‘Send’ button at the bottom. If participants don’t receive the invite within an hour, it may have gone in to their Junk folder.
League members then simply Sign Up or Login, then click on the link. They will be automatically entered in to the league.