Flash to fire off camera

AB2105

Hi, I have a Godox TT520 flash, which is great. I get fab results with it, especially if I use a reflector over it. I have been given a Godox TTL 3 meter cable and would love to use the flash off camera. How do I set it up? Do I have to use a particular setting on the camera? Do I need to use the pop up flash (I don't have another speedlight for the camera apart from the one I want to use off-camera)? My flash and cable are the same brand.

Help!