For the left and lower right ear cap, you could use epoxy, E-6000, or you could bolt them on. Here's a tutorial for bolting the ears on:Bolt Attachment Method
And for the upper right ear cap, if you have a rangefinder stalk there, you could make it removable for transportation by using the magnet method. Here's a thread on TDH on doing that, go to the 8th picture down to see how he attached his ear cap:Magnet Attachment Method
Also, here's Novall's tutorial on doing the magnet method, it's more in-depth than the TDH thread:Novall's Magnet Method
I personally just glued my earcaps on my helmet, although I wish I had bolted them on so that I could more easily transfer them to a new helmet after I upgrade, but I'm lazy.