After downloading the mod, use a program such as 7zip or WinRAR to extract the main folder of the mod.
Drop that folder into the mods folder which is supposed to be in the game's installation folder (don't know where that is? click here)
Extract the MW2019 Operator RDS file into mod_overrides.
CAFCW: Optional if you only plan to use vanilla weapons.
If you plan to use custom weapons like the HK433, SIG MCX, MK18 Mod 0, or AUG 9mm, you'll need CAFCW's offset values so the sight lines up correctly on custom weapons.
Install CAFCW by placing it into your mod_overrides.