When your threshold ramp arrives in the mail, simply remove it from the box and place in the desired location. Be sure to put the thicker end or the end with legs (depending on the ramp style) against the door frame and the thinner end facing the opposite way.
For adjustable threshold ramps, you will need to twist the bolt in a clockwise or counterclockwise direction to achieve your preferred height.
Some aluminum ramp models have holes in the thinner end which can be used to mount the threshold to the ground. To do so, begin by placing the aluminum ramp in the desired location. Using the ramp as a template, drill a hole about 2″ deep with a power drill, then secure the ramp into place with the proper screws.