FAN (Fan Access Network) Tokens allow you to participate in the FCFL. To quote the FCFL website directly:
"FAN tokens are the power behind fan interactivity and engagement in the FCFL. All activity in the league relies on FAN tokens, from voting on which coach to hire to real-time play calling during the games. The more FAN tokens a fan owns, the more control that fan has over their favorite team.
Fans can accumulate FAN tokens by watching games, calling plays, proving their knowledge, making team decisions and competing against rival fans. Certain top fans of the team that wins the title get a cut of the $1,000,000 and growing championship prize pool and bragging rights over the rest of the league."
As with all blockchain based tokens, there will be an ICO (token sale) taking place, where you'll be able to buy tokens directly from FCFL. This will take place on yet to be determined dates in early 2018. After that, you'll either need to buy your tokens on an exchange, or earn them through your activity in the FCFL app.