Installation of a battery monitor is straight forward. Here’s a picture of my battery shunt installation. You can use a piece of copper or just a short cable. The copper shown is a flattened piece of 3/4” copper tubing.

The cable on the battery post is connected to a second parallel battery and not any loads. Hence all current passes through the shunt.
The Trimetric 2025 is connected to the display with 6 strand light small gauge cable. It the cable runs along other power cables then you might need cable with 3 twisted pair conductors.