I was surprised to see I didn't have a KB on this process yet. Here is a step-by-step for adding your button art. The button used in the below example was a Sanwa OBSC 30mm red. Before we begin, let me say that clear/translucent buttons are a lot more delicate than their solid counterparts. My advice is if you haven't already added art to buttons you placed in your panel but placed the buttons, stop now. Its best to do the art with buttons you haven't used yet. The tabs are infamous for breaking. Even just now, I broke a tab to pull out an example button for this KB from my VS. You're welcome .___.
Step 1: With a small flathead screwdriver, apply a gently amount of pressure to the plunger tabs and push upward in one motion.
Step 2: Examine where any small plastic tabs may be dipping in relation to the plunger. Using your fingernail, pop the top of the cap off the rest of the plunger.
Step 3: slide your art into underside of the cap.
Step 4: make sure the plate under the art, on top of the plunger lines up with grooves and that the dipping piece of plastic is lined up with the plunger grooves as shown below.
Step 5: Line the plunder tabs back with the holes the fit in and also the plunger lines up with the inside microswitch.