Working with power tools, whether with wood or metal, is inherently dangerous. That means that working with power tools cannot be made safe, though the risk of injury may reduced to a low level if safety precautions are observed. If you are unaccustomed to reading operating manuals, make an exception for the manuals that came with your power tools. No matter how experienced you are, accidents may happen. Failure to wear OSHA-approved eye and ear protection is foolishness, not manliness. If you wish to perform this procedure but do not have the proper tools or do not feel competent to do so, you should at least be able to remove the focuser housing - a trivial task requiring only a metric hex wrench of the proper size - and take it, along with your bracket and RoboFocus motor to a machine shop and have them perform this work. Be sure to take your 1/4" X 20 socket-head screws and the attachment hardware (screws, washers, and shaft coupler) that came with your RoboFocus.
Not shown here: Although I have a bit of experience in drilling and tapping soft metals, before I undertook this task I successfully drilled and tapped a scrap piece of 1/4" thick aluminum to practice and gain confidence.