stop playing games on the computers
We're not sure why you don't want people using games on the computers, so we're not sure how to answer. Post a comment below and give us more info.
If it's because people get noisy at the comptuers - please notify a librarian who will ask the people to quiet down. You might also move to a computer in a quieter area.
In order to make computer use fair to all users, we use software that gives everyone the same amount of time, but each person may choose how to spend his/her computer time.