If you want to do it yourself, you'd get a colorimeter or spectrometer and then software that lets you use them to adjust your screen, like ArgyllCMS and DispcalGUI: https://displaycal.net/
The easiest way is to pay a professional. Hardware required to properly calibrate a display is too expensive to make any sense to buy it unless you don’t care about money.
You won’t get great results by downloading profiles from the internet because every unit is different coming out of factory.
There's a list of hardware supported by Displaycal here: https://displaycal.net/#instruments