Measure the space you have. A standard single car carport is 11 feet wide by 20 feet long. You may want to make yours wider, or longer; anything shorter or narrower may not fit your car. The height should be the same height as the eaves of your roof; the top of the carport will fit right there.
Make a diagram.
Measure it again. Measure twice, cut once. Purchase seven 4x4s and cut them to the length that equals the height of your carport. Purchase 2x4s and cut them as follows two at 5 feet 5 inches and 1 at 11 feet, these will be the back and front of the carport (be sure to cut them to your measurements). Then you will need 3 at 6 feet, 6 inches and 1 at 20 feet, these will be the sides. Next you will need 3 at 20 feet; these will be the roof supports.
Drive small stakes into the ground at the corners of your carport-to-be. Then drive a stake at the mid point between the two back corners. Do the same thing in the front. Then drive two stakes evenly spaced between the corners of each side. Run string or twine around the stakes. This will give you a string box.
Put concrete deck anchors into the ground on the outside edge of your carport. Place these exactly where you put the stakes.
Place the 4x4s into the deck supports. Also place a 4x4 at the front and back of the carport flush against the house. These will be the corners and center supports of the carport.
Use 2x4s to form the top. Screw the corners together as illustrated to provide strength. Place one 20 foot board between the two corners that are against the house. Screw this and the 4x4s into the siding of the house. Then attach the rest of the short 2x4s between your uprights, screwing them to the 4x4s as illustrated.
Attach the 20 foot roof supports across the top, lengthwise. You may cover this with corrugated plastic, or other roofing material.