Single-player offline leagues?

[MannStooka]

I can't believe I can't figure this out, but I'm wanting to set up a single-player league and I can't find a way to do this for the life of me. If I go to league portion, it puts me into the multiplayer section where I can create a team, but I need tickets to join a league? I feel like I'm missing something totally obvious but I don't know what it is.

Also, is there any single-player campaign aside from the human team?

[Duct Tape]

Hit play in a league and select Solo, should be the top button of the 2 that pop up.

[Dayblaze]

When you have your team ready, click the join league button. The very next pop should be just like Gunclap says, top is solo league, bottom is multiplayer league. Hit the top "solo league" button, after that you can choose from different league sizes. The opponents will be randomized.