The idea of the fantasy league is to allow fans create the best "fantasy team" they can, by selecting a total of seven real-life players currently participating in the CAL-I Counter-Strike season. 5 players are selected as starters, and 2 others are bench players. Then when game time comes, the better your team performs, the more points you get in the league. It's very similar to other online fantasy leagues for professional sports (baseball, football, etc.)
Joining the E-Sports Fantasy League is free, all you need to do is register. Currently, the league is in its BETA stage.
E-Sports Fantasy League | Fantasy League FAQ