Hard to stick!
Reading the other reviews it seems I wasn't the first person to buy these and think they didn't "stick" - I must've torn up four of them before I "gave up" and used micro-brads to fasten them to pages.
Eventually, purely by accident, I managed to free the paper backing from a tab.
It takes a lot of bending and twisting to get the paper free, but once you figure it out they're decent little tabs.