Modify the camera mount so that the top slot is wide enough to fit a lego plate. Fit the camera module to it, then fit the whole thing into the roof section mount. Fit the camera cable between the Pi and the camera module. The standard cable is a bit too long - a shorter one works better.

Build up the rest of the lego parts, inserting the PCBs and wiring them up as you go.

Wire two 18650 battery boxes in parallel and add a connector. Slide into the hole in the back and connect to the power PCB. To stop them falling out, add a couple of lego bricks to the hole.

Install Raspbian Lite on a micro SD card and configure it to run as a wifi hotspot. Install piroverd from the github repository along with dependencies (gstreamer, libi2c-dev etc). Configure it to run at start up.

Build pirovera APK from github and sideload it to your Android device. Connect to the Pi wifi hotspot and run pirovera. You should now be able to drive your pirover.