All right, keep your feet on the stirrups and your hands on the reins. [he hands them to her.] Something like this. [and then he positions them into a basic form. eh, not like they're going for any actual professional style or anything so yeah, whatever.]

If you want him to move forward, just nudge him a little with your heels. If you want him to stop, just pull on the reins. That's pretty much it, really.