So i noticed that my files in my C:\Program Files\KiCad\share\kicad\library are really outdated compared to what i have found at https://github.com/KiCad/kicad-library/tree/master/library
(i just installed the latest version of KiCad)
After i wasted 5 hours googling how to update my outdated files i decided to manually download “atmel.lib” and “atmel.dcm” from github and put them into my mentioned …\kicad\library folder.
It owerwrote my older, much smaller “atmel.lib” and “atmel.dcm” files.
Then when i loaded KiCad and opened a .sch file i got an error message regarding those two “atmel” files saying stuff like “io error … not an eeschema library”
How exactly did you “manually download” them? If you did “Save Page As” in a browser, you might have got some bad data in the file.
I find the simple and reliable way is to download the zip (option 2 in @keruseykaryu post). Note there can be problems copying files into c:\program files due to Windows UAC.