Measure out a 4-foot by 8-foot space for your PVC greenhouse. Alter these dimensions to fit your space restrictions and needs.
Hammer in a steel spike with a sledgehammer at each corner of the space and every 2 feet along the 8-foot sides of the greenhouse. Use steel spikes or iron rebar posts that are 1- to 3-feet long. Each spike should have 6 to 8 inches buried in the ground for a firm hold.
Dig out the grass in the space you have measured out with a shovel. This will allow you to plant and garden inside the greenhouse. Remove 1 to 3 inches of sod, including rocks, roots of other plants and any other debris in the area.
Cut your PVC pipes with a saw so they will span the 4-foot width of your greenhouse, and add 2 to 3 feet to that length so they can be bent to form arches. Bend the pipes so they form equally sized arches.
Put the PVC pipes over the ends of your steel spikes. Add glue to the pipes to keep them in place if necessary. Work with a partner to put the pipes on the spikes.
Cut plastic sheeting with scissors so it will fit over your greenhouse with 8 to 12 extra inches on each side. Work with a partner to stretch the sheeting taut over the greenhouse and attach it to the PVC pipes with small clamps or ties. Puncture the plastic sheeting with scissors to attach ties if you use them. Place bricks along the edges of your greenhouse to hold the plastic sheets in place.
Add a layer of compost and topsoil to the space inside your greenhouse before planting things in it. This will replace the sod you removed and create a healthy environment for your greenhouse plants.
Water the plants inside your greenhouse on a weekly basis, or more frequently if the temperature in the greenhouse rises too quickly.
Remove the plastic sheeting every fall after the growing season has ended, and replace it with new sheets in the spring.