First thank you for trying to help them.
When I get a rescue horse in that has been misused, I will turn them out with my herd and just let them be horses. They soon learn that I provide food, affection, and discipline. If they want food, they need to come to me for it. It starts them accepting humans as good.
You can go set up a lawn chair and read a book with a bag of carrots on your lap. If the come close, toss a bit of carrot. Soon you'll have their trust.
Once you have them following you, start working them in the round pen.
The thing with these horses is that if they have been misused or abused, you have to be careful to push them far enough each day that they are learning and coming around, but not so hard that they slip back into the "abused" mindset. It is a delicate balancing act.
Spent a whole hour today laying in a pasture, waiting for a sparkling vampire to show up. Alas, I woke up and looked over, only to find a mound of horse crap. Sigh.