Manage those cables!
You will need the following 3D Printed parts:
DIY CoreXY 3D Printer | LayerFused X301 Part 3 - Electronics Mounting
There really isnt a step-by-step for mounting the electronics in the electronics box. The box is large enough to accomodate a number of different configurations. The main thing to keep in mind when mounting and installing the electronics is that cable management is important. The Signal cable was used with this in mind.