The RPM is designed to mount on the inside of the non-drive side crank arm. Placing the RPM on the outside of your crank arm will result in interference with your feet. Likewise, installing the RPM on your drive side crank arm will interfere with your drivetrain.
When placing the RPM on your crank arm, be sure it does not make contact with the frame as your crank rotates around. Once a suitable position is found, use either the 3M Double Sided Adhesive or the silicone mount and zip ties to affix the RPM to your cranks. The RPM should be flat against the crank and oriented either directly parallel or perpendicular to the crank arm.