Reddit reviews What is Human Echolocation?: An Emerging Mobility Concept for the Blind

Here's the book by Tim Johnson, He also has a blog but it hasn't been working for me recently, might just be a problem on my side. He's also super responsive to emails, as is Daniel Kish.

They have lessons and steps, but I've never been able to advance past the most basic (clicking at a board or flat object until you can tell when you're facing a wall)

Good luck! If you get farther then I did, let me know how you did it haha