Decide on the shape of your trellis. This will depend on the sticks you have available, the wall space and the type of plant you want to grow. Most trellises are either fan-, square- or ladder-shaped.
Construct a traditional fan-shaped trellis by arranging six or seven similar-sized sticks in a bunch. Tie one end tightly with twine then spread the sticks out on the ground in a fan shape. Tie short sticks across the width of the fan to brace the shape and make it solid. For ladder- or square-shaped trellises, lay the sticks out on the ground in the required shape and tie them together with twine.
Lift the trellis into position against the wall and mark the points for the screws to hold it to the wall. Put in at least three screws -- more if your trellis is heavy. Drill the holes, put in a wall anchor and put in the screws so that the heads protrude at least an inch from the wall.
Tie the trellis securely to the screws with wire. Locate your climbing plant in front of the trellis and tie the stems loosely to the trellis with twine. As the plant grows, continue to tie the stems until the plant can support itself.