You simply find a suitable safe 'curve' place the car in low gear, on a DCT use sport+ and select a low gear so it stays in that gear, then accelarate to 25ish mph on the curve and apply more throttle/wheel till it drifts, then control it on the throttle.
You wont be able to do it like the amazing drifting videos we see as those cars are often set up suspension/diff wise to enable drifting, splayed out rear wheels is a classic mod ......
I would buy some cheap tyres and put them on the back as well, anything that squeals when you corner in the multi storey in hot weather will do, (high teflon content lol)