It can be extremely dangerous for you and the horse to ride with side reins on. If anything goes wrong you can not get rid of them. They are going to stay there.
As to your question on how to get you horse on the bit properly, you can't do it with your hands alone. In the beginning you will just want a forward and under control gait. Then, once you have mastered that you can move on to bending, attempting to get your horse to be supple. Once your horse is supple and engaged in the hind end, the head will begin to follow.
This, of course, will take a long time and I suggest getting a certified, reliable dressage trainer.
"You know, for as long as I can remember, I've had memories." ~Colin Mochrie