Hi, I had to change the shape of one pad (in the IC Package the pin 1 is a square so as to help correct orientation when assembling the board). I had to right-click, find the library file name and the name of the part; then open the library, search for the package, open it, change the shape of the pin, save. Then back to the board and update the library.
Maybe there is a shortcut I am not aware of, but I would suggest adding an "edit library" or similar in the right-click menu that would open the component for edit and do the update on exiting.
Regards!