This must be simple but I cannot figure out how to change the wiper blades.

Help!

 

Some change the whole blade.
Some squeeze the clip on the bottom and pull out the blade and install the new blade - replace with refills.
Some press the red button(s) and blade comes off and new one snaps into place.
It all depends upon the brand/style used, whether OE and all up to replacing the blade as with a J-hook arm.
Picture of existing arm/blade would be good.

 

OP, if you have stock wiper arms than the ANCO 20-15 or AC Delco 87150 are replacements

https://www.rockauto.com/en/moreinfo...321232&jsn=449