The base plate is split into two separate pieces that are joined together with screws. The plate with tubes connects to LEGO studs. Join the two pieces together at the flat sides. While holding them together, insert and fasten an M3 x 12mm (flat head) screw. The screws heads needs to be flush with the surface of the base plate. The mounting holes are chamfered and designed to recess the screws. Repeat this progress for the four mounting holes.
While holding the base plate, insert one of the long standoffs and twist to fasten onto one of the screws. Tighten the standoffs by hand for each of the four screws.
If you haven't put these two together yet, now is the time to do so! Grab the pcbs, screws and standoffs that came with your crickit. Insert a screw through the bottom of the CIRCKIT board. While holding the screw with your finger, flip the board over and twist a standoff onto the threading of the screw. Twist until tightened. Repeat the process for all six mounting holes. When your done, place the CPX over the standoffs and line up the pins. Be sure they're in the correct spot with matching labels! Insert and fasten the machine screws on top to secure the CPX.
Place the Crickit PCB over the standoffs and line up the mounting holes. Either set of four holes can be secured to the standoffs. Pick your orientation and insert machine screws through the mounting holes. Fasten the screws until tight.