Don’t worry be happy, it’s part of the fun…..
install everything on a flat surface in order to see how it looks and be able to measure where exactly it has to be; post a picture of the initial set up.
First step: tie to the ground the front and the back of the bike sitting on it (without the stand), that will give you the final height of the frame, make sure it sits strait; bring the chassis next to the bike, and determine the exact position of the sidecar wheel, tie the shock absorber half way, make sure chassis is levelled .
Then and only then, you will be able to figure out where and how to attach and start fab…
See the blue tie down on this picture.