Right side bumper plastic step piece - how to install

Hoping for some advice!
This is my hubby's 2nd gen Tundra. He lost the right side bumper plastic step piece (don't know the "real" name for it - hope the pictures suffice!), so I ordered a replacement. I think it should slide onto the white plastic nub piece first, then snap down at the back. But I can't figure out how to get it to hook onto the plastic nub piece (see first pic.) I don't want to force it because I don't want to break either part

Edited to add: Oh fine! As soon as I finally gave up and posted this, I figured out that the little white nub piece pops off. So I slid it onto the step piece, and then popped the whole thing onto the bumper. The white piece seems as if it will pop back off rather easily, so I might have to find another to support it/stick it on...silicone goop, maybe?