How do I get my horse like this?

I was going through this proplem recently, too. My gelding had been going behind the bit on his own, and it was a problem. It might take a while to fix and it might REALLY bug you, but it really helps. Don't ask for a head set at all. Just keep a light but constant contact on the reins and just drive your horse forward from the hind end. Your horse will really have to use her hind end, and if she's never been asked to use it before, it will definitely be new to her and she'll most likely become fatigued sooner and might be sore. If you focus on impulsion and power from the hind end and just keep a contact on the reins, then the headset will come later. :)