It should be as simple as undoing the skewer then pulling those silver end caps out, you may have to put a flat head screwdriver into the gaps between the pinch bolts and give them a gentle ply to loosen it's grip on the silver end caps.
This is how the axle looks inside, you can see that the silver bits don't actually screw in to anything they should freely pull out, once they are out then you slide the black thru axle out with ya fingers or u may have to tap it out with something if it's in really tight.