Can't see any pics but there are the following attachments from outside edge to the middle.
1. Outside edge: + headed screw/bolt with
captive "nut" (bit like a wing nut) inside a nylon fixing, with a rectangular "washer" that rusts like crazy. The bolt also tends to rust into the "nut" and then the "nut" breaks away from the nylon fixing and the whole things becomes useless.
I bought some "nuts" from Fiat a while ago, not showing as not available, part number 46304611. The screw/bolt is 13276211 and the washer is 46305680 (expensive!)
2. 3 screws (early) or allen headed bolts (later) with thin washers fixing the side/fog light/indicator units. Middle one is more fiddly and often gets "lost"
3. Flat headed screw, need a T30 bit, screws through upright part of bumper either side of the radiator into a threaded hole in the slam panel bracket thingummy. Also often rusted to bu99ery. ePer appears to show a spacer but I've never seen one?
4. Large screw/bolt that goes through top/side/centre part of bumper (kind of wraps around the slam panel edges) with thick washer.
Here's
the full set (with only two screws each side for the lights, one with an extra washer). Also showing one of the "pins" that attaches the radiator grille to the bumper.
And then of course you have the bottom fixings that secure the bumper to the undertray, but they belong to the undertray.