Pick up large tree branches, rocks and other items that are in the area you're going to mulch. Pull weeds and any other existing vegetation that you don't want to grow there.
Rake the area to clear it of rocks, twigs and other debris. You'll also want to rake the dirt to level it as much as possible.
Spread sheets of newspaper on the ground to cover the area. After you put down the first layer, wet it thoroughly with a garden hose. Wet each additional layer before you apply the next one. The wetness will help hold it in place.
Dump the desired amount of mulch on top of the newspaper to keep it free from pesky weeds. Carefully spread it around to the depth you want. Your plants will now be protected because the newspaper will block weeds from growing.