Specifically, go to the Library Manager under Tools ==> Manage Libraries
Scroll down (it takes a while and sadly the "filter your search" function simply does not work!) to find the "hd44780" library by Bill Perry and install it.
Then you will find "HD44780" in your examples.
For I²C, the old LiquidCrystal library is useless.
OK, looks like you have found it but mistakenly gone to "Other Libraries" which is useless.
OK, found it for you:
