I was wondering if anyone could help me; I need my horse to use his backend more, but I'm not sure how.

The very essence of Dressage training is to engage the back-end more - and a few very brief answer would be: Use more leg and seat....
Do transitions......
Back-up and depart exercises.
Leg-yielding, shoulder-in....
Do you spend enough time warming him up (suppling, relaxing, stretching so he is using his whole body?)
Trotting poles........


However, to understand better what exactly you are after and when, we would need to have a little more information.

Tell us about you and your horse
- What level are you and your horse training?
- Do you feel your horse is not responsive enough to
your "forward" aids?
- Do you ride with spurs/whip?
- Is he just lazy?
- When exactly do you feel there is not enough
engagement? Why do YOU think that is?

Well to start with my horse has recently just come back after being laid up for a month or so. He is limited to light work, however he is a very energized TB. He was first being lightly lunged, and now I've been giving him light hacks. He has been doing well, except for the fact that his energy gets the best of him and gets playful or spooky. I try to use my legs lightly, and I've tried half-halts to use his backend better. I think he's just so happy to be out working that he doesn't really pay attention to his work; the vet said to walk him around and then go straight to the canter on the left lead(he injured his right hoof). He's very responsive to the aids and is a very foward horse but not difficult to collect. We have to stick to light work for two weeks (and 20 min. of work is nothing to my horse!). Thank you for your help!

Your horse is just coming back into work after an injury?
Why your vet suggests to walk him and then to go straight into a left canter leaves me puzzled?! It doesn't make sense.
If this horse can not be ridden in all paces and leads, he is not ready to be ridden.

Assuming the above is a misunderstanding and the horse is healthy and sound on all legs, you should continue with light work and give him a balanced diet so his energy level is compatible with the work he is getting.

I suspect "forwardness and engagement" is not really the problem. I have the feeling it is more a problem for you to contain his energy and translate it into some sensible work?

Trot work is your most valuable tool to channel energy into rhythm, relaxation, contact, impulsion, straightness and finally collection.
To start, allow him to stretch down and out in contact.

It requires quite a bit of self-control to help him maintain a steady calm rhythm but once you both have come into the "swing of things" you will feel how he will feel more relaxed and starting to use his whole body, lifting you up and along with him.
This is the moment when he is using his back-end.
When you feel him pushing/swinging and stepping through, maintain this power with your legs and seat and start "receiving it" in your hands. He should be taking the contact that you offer him. It should feel "positive" but light on both ends, yours and his.
If you still have the feeling of being lifted up and carried along, I would bet my hat that your horse is using his back-end!
Have fun!

nm