Play offline with bots under the Easy difficulty setting. Choose the Bank map because it is open. Choose the terrorist faction. You will automatically spawn with the bomb. Instead of planting it, take it with you up the first ladder, then go to the left roof and kill all the counter-terrorist players that you see on the street. Drop down and kill the rest of them, who still should be nearby. With luck, your friendly bots will not have killed anyone before you. If not, try again. Note: You will get new guns and grenades on each round.