no worries! It took me a while to figure it out and when we're cooking around it still takes effort sometimes to get the result.
First off i started just standing still on her and i would pull the reins out to the sides and up a bit, hold steady and the second she gave to the pressure and dropped her head (even the slightest try) I released the pressure and told her good job and pet her.
Then ask her again and ask her for a little more of a drop, so hold the pressure to start, she drops slightly, release and ask again right away to get it to go further .... hold pressure until she drops a little further, then release immediately and tell her she is a good girl.
Eventually she will set her head when you ask with both hands, at which point (and some people may start using only one hand right from the start. I am a firm believer that what the horse responds to and gets the job done, go with it and refine later (but if she responds to one hand rather than 2 youre aving a step)) you will start asking with one hand...if she doesnt respond to one hand, then lift the other with it, and when she responds pat her and do it again with one hand...do this until you get a result with one hand).
From there ask her to set her head while standing still, then hold it and ask her to move forward (now that you've set in her head what lifting your rein means she should respond while moving, you just hold the pressure if she doesnt until she gives). While you're moving, if she lifts her head just politely ask her to drop it again, when she responds release the pressure.
The more she understands, the more subtle you can be (on a good day with sable when she is focused, i just have to turn my wrist slightly upwards to get the set) on a bad day i lift one rein up a few inches...but when we started i had to have both hands stretched on either side of her neck and lift gently upwards...so it takes some time)
Anyways, let me know how it goes and it if helps any!