It is time to get supports around the tomatoes. The growth of a garden at this time of the year is very fast. Those small tomato plants are going to be big tomato plants in a short time.
The first part of installing a cage in is light tillage around the tomato plants. The roots of the tomato plants are near the surface. Just move the soil about an half and inch deep. Tillage around all of the plants in the garden at this time is important. The weed seeds have germinated. When the soil is disturbed the weed roots lose contact with the soil and die. This means you do not have to pull many weeds.
After tillage add the cage. With the EZ Tomato Cage just let the legs slide around on the rings and then set the bottom of the cage around the plant. EZ Tomato Cage have an option to add extensions, so it is important to protect the top of the legs. I use a hammer and a board to drive in the legs of the cage in to the ground. Hold the board on top of the cage and then hit it with the hammer. A rubber mallet would also work.