Just sharpen the two blades that you can already see a bevel on(this would be the two edges that you can see in the photo above). Four edges have a bevel four do not.
Use a double cut file laying the file across the two blades and pushing back to front. Then go to a stone either back to front, or front to back. You could also use a marking pen on the blade edges first. Then you can tell when the whole edge is removed evenly when all the marker is gone.
Look straight down on the edge, there should not be any flat shiney spots, just the edge bevel. You can feel a burr with your finger on the back side of the beveled edge, or pull a cotton ball or Q-tip on the back side of the edge. If there is a burr, fibers will be snagged.