just watch him do it. if that didn't help(I don't think it did anyway XD) follow these steps!
1) Get into a slightly slacked mach 5 mount where the yoyo is in the middle of a v shape thing., but don't revolve even once! (if you want to make it easier, you can to get wraps).
2. pop it into the air!
3. Move the left hand forward, and the right hand backwards via under the left hand.
4. You are in a split bottom mount if done right.
5. Scream in accomplishment.