Look to see if your grass is a cold-season or a warm-season variety since both types have their own growing seasons. If you fertilize the lawn when it is not growing season the grass will be unimproved and you encourage weeds to grow. Cold-season grass grows in the early spring and early fall. Warm-season grass is best fertilized in late spring and late summer.
Fill a spreader with fertilizer once your lawn has been mowed. Read the back of the bag to determine how much to use based on the size of your lawn.
Set the spreader in accordance with the fertilizer instructions so the lawn gets the appropriate amount of fertilizer per square foot. The setting determines how much fertilizer the spreader is dropping as it moves.
Walk the spreader across the lawn in even rows to drop the fertilizer down on the lawn shortly after mowing.
Water the lawn either manually or with a sprinkler system to help the fertilizer sink into the soil so the lawn reaps the benefits of it.