If you've got a problem with moss growing in your lawn, here are two thing you can try:

1 - Moss likes the shade. If the moss is growing in an area that is very shady, try taking steps to reduce the amount of shade. If the shade is caused by tree, try removing some trees or thinning the branches so that more sunlight gets in. If you can increase the amount of sunlight in the area, this will make it harder for the moss to grow and easier for the lawn to grow, so the lawn will take over and crowd out the moss.

2 - Test your soil. Moss does well, and grass does not do well, in soil that is acidic. If your soils tests out as acidic, add lime to the soil to reduce the acidity. This will hurt the moss and help the lawn.