I see those, and I see the corresponding listing in the league listing. I just normally enter the number of the theme league, and since these leagues are listed as private, I don't know how to enter the league.
I'm sure I'm missing something really basic. I was trying to enter a team into "2018 WIS Championship - League 1B" 65 million. I don't know how.
I entered MLB58881 into 'Existing League', and the error came back reading 'The specified league is either full, does not exist, or it is a Spring Training League.'