Prime the cedar post, then paint it.
Drill two rows of pilot holes every 18 inches down the back of the cedar post and equidistant from each edge of the post. A pilot hole is a small hole that you drill before you widen the hole to fit a larger item like a screw.
Attach one section of lattice to the side of the cedar post, using the 1-inch screws, which you should screw into the pilot holes. Lattice sections can be quite flimsy and must be anchored to stronger pieces of wood to keep them secure, so it is better if two pieces of lattice are connected with a sturdy piece of wood.
Attach the second section of lattice onto the back of the post in the same way you did in step 2, but use the second row of holes.
Paint any wood surface that you might have damaged while you were joining the lattice pieces. Also paint the screw heads on the back of the post for a uniform look.