NBA 2K10

Bench points are points scored by players that didn't start (they started the game on the bench). When the game starts, score a basket or two and then bring a player off the bench into the game. You can do this by pausing the game, going to Coaching and then Substitutions. Bench players might also be automatically subbed into the game if you didn't turn off Auto Substitutions in the Coaching Options menu. You don't have to score 40 points with one player off the bench, just 40 points by players that didn't start.
If you create a team with all of the players that have their own achievement, you will get this by getting all of their achievements in one game
You will unlock the achievement right when you get the 40 points.