Off-camera flash is actually quite simple. All you need is a speedlight flash, a trigger/receiver to wirelessly fire the flash, and definitely your camera.. You could also include a reflector, umbrella or softbox (whichever is available) and props if needed.
In this case there was no wireless receiver and so I had to use my on camera flash to trigger the speedlight (off camera flash). In order to do so, your speed light needs to be a slave and you want to turn down your on camera flash so it doesn't affect the scene greatly. After that i's just firing a couple photos to work out whether the flash power is too high and working out the direction of your light. And if you are wondering, this technique can be used outdoors as well, so do your research and give it a try.