1. Hop on the further edge of the trash bin from the T-Spawn and get close to the wall
2. Aim at the point where the vertical extension of a line behind the left trash bin and the horizontal extension of a line from the top of the pillar where stairs turn left, cross paths. Or simply try to spot a pack of leaves shown in the video and aim in the middle between the first and second from the right.
3. Run briefly on the trash bin you're standing on and before falling from it, Jumpthrow your smoke grenade.

Note: Your timing doesn't have to be perfect, same as the place where you put your crosshair. Try to follow the general steps shown in the video.