Easy.
First study the the setup and remain calm.
Next.... notice that instead of the metal you are looking for (to squeeze) there is just rubber, BUT in fact the rubber protrudes in such a way as to keep the whole rubber refill in place. You will find this on the last clasp that holds the refill.
Note: Sometimes, they load these in from one side or the other, find the side which has the rubber 'stoppers'. i.e. It doesn't matter which side you start from, so someone can load them differently. If original, they should have started from the drivers side.
So once you find the side with the rubber stopper, hold the entire arm and pull the rubber refill FORWARD (as if you where initially loading the refill) FORWARD as to say you are passing the last holder/clasp.
You may have to tug hard.
Once you do this, you will get past the little rubber stopper.
Your refill should be loaded on all the clasps except this last one and you can now simply pull your refill back out as you would expect.
Hope this makes sense.