This is because you are not on the right screen.
You went Manager Options and turned on Commissioner Mode. Good. Now though you're just playing around with subscriptions. That's just what comes in your mail and has nothing to do with adding a team.
As the manual, says, you need to go to League > EDIT. Meaning on the top where it says NHL click on that, then scroll all the way down to EDIT.
Further, if you're still not sure; watch this video and follow along:
https://www.youtube.com/watch?v=CxACrnQuvTE