This can be a bit tricky for people who choose play as lone wolves, but work with your team and it should come fairly easily. "Team Points" are awarded for essentially being a good teammate in ranked matches.
***The 20 points must be done all in one match.***
Getting assists on kills, capturing flags/objectives, and defending flags/objectives as a team all give team points (as long as you are in close proximity to each other). (As with virtually every shooter, sticking together pays off!)
If you're not boosting this, be sure to be in game chat or in a party with your team to synchronize your efforts. Stick together and cooperate.
Edit 1/26/2016: I'm unclear why this would get a negative vote, so please let me know if something is wrong.