These mounts are first bolted to your engine with the proper hardware. I would recommend using lock nuts instead of compression style washers.
After installing the mounts you need to install the engine with the transmission into the car. Bring the engine as far back to the firewall as possible without hitting it, and leaving @ ¾ to an inch clearance. Then raise the engine as high as possible until you bottom the transmission against the car or truck floor.
Then allowing at least an inch clearance between the floor and the bell housing level the engine with the intake manifold installed on the engine this is your leveling surface. Once the engine is level front to back, then level it left to right.
Placing a small jack under the pan is an easy way to accomplish this. Make sure that you now have an equal distance on each side of the engine and the vehicle frame.
Take a piece of cardboard or heavy paper and cut it out to the same shape as the rectangular tube mounts (these have the bushings installed ) and come in the kit. Trace the tube unit and using the template make a hole in the center of the cardboard where the attaching bolt goes through the fixed portion of the engine mount.
Now you can use the template to give you the correct angle to cut the 1 X 3 tubes to the frame. This is done by bending the cardboard at the angle that the frame forms with the template attached with the ½ inch bolt going through the center at the bushing end.
Once you get this angle cut the rectangular tube at the angle taken from the template.
Install the cut rectangular tube to the fixed part of the engine mount. Make sure everything is still level and tack the mounts to the frame. If you now need to check other clearances you can leave the mounts tacked until you are ready for the final installation.