[Leo_The_Lip]

Easy enough if you use the expansion tool to do so.

Essentially it is located in the league settings. you can only do this in the offseason, so right after the WS is the best time. The wizard will ask you what you want to do with teams. In the example of the NHL, you would place the six existing teams in one league, the expansion teams in the other. The wizard will establish minor league teams for the six new franchises. I would check to make sure the schedules are generated properly the first time. I had the wizard fail to schedule games for the expansion MiLB teams the first time I tried this, but I think that was me.

then hold the expansion draft after deciding how many players will be protected. I'd recommend you play for 10-20 seasons first in order to generate enough players for expansion, the set a maximum number around +/- 20.

Now you're good to go. You'll need to repeat the wizard in offseasons where the teams are added. The wizard allows you to change the overall divisional structure at that time.

The process is reasonably intuitive, however I recommend a dry run that you'll delete when you finally realize what you muffed the first time.