Measure the space around the door including the width and height. Add 4 inches to the width of the door.
Cut the veneer into 2-inch wide strips, or order strips precut to your specifications. Use the door measurements to determine the length of each piece; two long strips for the sides of the door and one strip to cover the width of the door. Use a veneer saw -- if you have one -- or a craft knife. Put a yardstick on the veneer to use as a guide to create a straight cut with a craft knife.
Paint or stain the veneer strips if you desire. Allow the strips to dry overnight.
Install the veneer on one side of the doorjamb. Peel the back off if there is a sticky back or use finishing nails and a hammer to hold the veneer trim in place. Hammer a finishing nail through the trim every 12 inches and at each corner. Repeat the process to hang the veneer on the other side of the doorjamb. The trim should go all the way to the floor and end at the very top of the door.
Put the final piece of veneer trim along the top of the door. The trim should fit flush against the door on both sides. Hammer finishing nails into the trim.