If the sprinkler is not spraying correctly this may be due to the head needing to be cleaned, adjusted or replaced. It may also just be a clogged screen. If these are pop up sprinklers, you will need to pull the pop up portion up to be able to unscrew the head. You will be able to check and clean the heads and screens with the heads off. Once done, screw the heads back on and adjust spray if necessary.
You may need to replace the entire sprinkler if the sprinkler body itself is bad or the internals are malfunctioning. This is a pretty easy task and will consist of uncovering the malfunctioning sprinkler, unscrewing it from the riser and screwing the new unit on. Once the old sprinkler has been removed, check the riser to be sure it is intact and will not be a source of a new leak once the new sprinkler is installed. Install the new sprinkler and then adjust the spray pattern to cover the area needed. Test your work and readjust as needed.