I just did this on mine, and after I pulled one wheel/tire to get to the hub, I felt pretty dumb. That little "center cap on the center cap" pops off with a screwdriver as The Kulas stated. Then under that, there is a black rubber dust cap that you also need to pry off (and replace after the greasing, which is even more fun.) That will expose the zerk fitting for greasing. Luckily, the remaining three were much easier!
2015 XLR Hyperlite 30HFS5 (mods being performed regularly)
2009 Salem LA 292fkds (gone)
Nights- ('12)23 ('13)23 ('14)15 ('15)31 ('16)25
2014 Harley Davidson FLHX (XLR cargo)
2014 VW Jetta TDI (diesel sipper, camping support vehicle)
2011 Ram 2500 CC 4X4 CTD, B&W Companion (toy hauler hauler)