I am not sure just what style of blade attachment you have.
If you still have the original coiled-spring over the pin attachment, then they are the BEST and super-easy to remove/install once you learn the simple trick.
If your's is that style, simply push downward on the exposed bit of the coil and the blade will slide right off the pin.
Look at the top-center of the metal blade and you should see the coil that I speak of.
Using a short-fat-wide straight-bladed screw-driver, press the coil downward, toward the inside of the blade, while applying a bit of pressure in the "off-the-pin" direction; the coil will align and therefore release.
Once you manage to accomplish this once, it will forever-more be simple.
It is far harder to describe than to do.
The original style of attachment is far more secure than any of the generic fit-all styles.
Myself, I go a big step further and retrofit genuine heavy-duty blades/arms such as used to be found on big trucks ( it was a terrible disappointment when I started seeing wimpy car wiper-blades on big trucks; is nothing sacred anymore ?? ) and are still in common use on locomotives, planes, and ships; no more of those wimpy string-of-rubber wiper-blades for me.
In fact, I just today swapped a set onto the wife's 1991 Dodge/Cummins.