Please refer to the video below, the front mud flaps just take a minute each, the rears just a couple of minutes.
Note:The newest version of the rear mudflaps have an additional mounting point (not shown in video) that hooks over the screw that protrudes into the rear wheel well - that's what the extra nuts in the box are for :-)
As noted in the video, the rear bolts thread through a weld point that's sometimes quite weak. If the bolts seem to be quite tight, or feel like they're binding, apply some WD40 or similar as you remove the bolts. Just go slowly, as as mentioned, if you're concerned about breaking the weld point, it's never a problem to return them.