Keeping possession of the ball will lead to more scoring chances, and limit your opponent's chances of scoring. If you encourage your players to use the passing game instead of booting the ball long, you'll get them playing top-class football - just like Barcelona with their tiki-taka pass and move style of play.
To do that you need to improve your player's ability to keep possession, even when under pressure. It's also important to get players talking and working on their communication. By talking and telling each other where other players are, it'll become a lot easier to keep possession. Develop their movement off the ball as well as their control when they receive, by using the small group possession drills and small-sided game videos below.