In general:
New PC specs?
Make and model monitors? Same make and model?
Read the GPU's User Guide/Manual. Also read the monitors' respective manuals.
What options are available? Will the build support all of those options?
If necessary:
Right click an open area of the desktop to access the GPU's control panel. Learn what options and configuration settings are available.
Use "WIN " + "P" to familiarize yourself with dual display "PROJECT" options.
Start simple.
Get the PC/GPU, monitors/display to all first work at the default settings. No overclocking etc. Then, go one step at a time towards the required, desired end configuration.
Not a "best way" answer per se.
However, taking a close look at everything beforehand may save you some time, effort, and frustration if all does not work as required.