Rake up all of the mulch and leaves that are currently in the established bed using a rake or a hoe to fit in between closely spaced plants. When raking, make sure to only remove the mulch and not any of the dark underlying soil, which is good for the plants.
Scoop up the removed mulch and place it into a wheelbarrow. Push the wheelbarrow to a compost area and dispose of it.
Place the roll of landscape fabric at one end of the established bed in between the plants. Set a rock, brick or other heavy object on the end and unroll it all the way to the other side of the bed. Cut off the excess fabric with scissors.
Return to the starting location and place the roll on top of the first layer, overlapping it by at least 6 inches. It can overlap more if needed due to close spacing of plants. Unroll the second layer to the end of the bed just as you did the first.
Continue installing overlapping layers of the landscape fabric in between each row of plants until all of the soil is covered except for the thin areas where plants are growing.
Insert landscape stakes or garden staples into the edges of the landscape fabric using a hammer. Space each one at least 3 to 5 feet apart.
Spread a 2-inch layer of fresh mulch in the established bed using a rake, making sure that all areas of the landscape fabric are covered.