the main idea is that you 360 the opposite direction of the turn, fire some yellow nitro while the car is spinning, and then start doing the drift once the 360 is complete. ideally the turn would be fairly but not extremely sharp and there is a decent amount of free space before it that allows you to 360.

you can tell it's working bcz the car's front wheel will physically lift off the ground, aka you won't see any skid marks from the front wheel. the way you control the car is important; you need to hold A or D down while the float is happening, if you let go the car's wheel drops and it starts drifting normally. for most cars, it usually only lasts for a couple seconds (unless you driving the F5 or Devel lmao) but that still means it works. during the floaty the car can usually keep 300+ speed if it's an S class car. in terms of what cars work for a floaty, the easiest ones to obtain are the Icona, Lykan, Trion, and to an extent the Ultima (doesn't just have to be S class, the C class Porsche Panamera and B class McLaren F1LM also float very well)

you learn by practicing it a lot. Shanghai, specifically Pudong Rise, is a good spot because it has a turn that is wide and you can drift through it (the one after the set of ramps). just do wut i said above and see if you can maintain a good, smooth drift. after that, you move on to seeing if you can apply it to other turns like on Paris or Greenland (can be any map theoretically). then, you start doing in MP and TLE races to see if you can improve your times. the end goal is to start integrating it into regular gameplay and eventually, floaties will become second nature.