By default, each Challenge submission awards the player 10 to 20 points (depending on the Challenge type). However, if you would like to award even more points for especially difficult Challenges, you can do so, too.
On the Topic Manager page, select a Challenge and click on it.
Scroll down. Under the "Other Options" tab, you can assign the number of points you want to award to your players, per submission. You can also assign a number of points a player will receive if someone else 'likes' or vote on their submission. See: How do I vote for another player's submission?