I'd recommend studying some existing macros and spending time recreating them. Starting with simple use-cases of the macro and working up. Repeat this with a few macros and you'll eventually learn how they operate. Let Over Lambda is also a good (opinionated) book on macros (most of the book is available for free), and of course there's PG's On Lisp (jump to page 95 in the PDF if you're already comfortable with Lisp).
Are you simply staring intently at the macros, trying to make sense of them, or are you actually utilizing the macro-expanding feature in your editor? Or perhaps you're grappling with writing macros yourself? Macros can be tricky, which is why Clojurists often avoid creating new ones unless there's a compelling reason to do so. There's an old book called "Mastering Clojure macros", it's tiny - fewer that a hundred pages. It helped me back when I was learning Clojure.
