Single DIN In Dash

Since my old shaft style stereo doesn't work right, I got a nice little unit that's single DIN. AM/FM/CD/Bluetoof/AUX/USB....."all dat". I mean hell, I had to cut the dash a little for my old shaft style unit.....although it would be hidden with the original radio......but I figure screw it, I want something NICE and modern since this car is gonna be a cruiser. So here's my question. I cannot get my head around how the sleeve installs and secures in the dash hole. The instructions say something like "choose the appropriate tabs and bend them down to secure" or some such. I see the tabs, but I cannot get my mind around how that works.....since I've never done a conversion. I've worked on some that were already single DIN, just not converted older stuff. Can someone clear it up for me? A picture or three would really help.