The error message says:
error: variable ‘fiveLetterWords’ must be const in order to be put into read-only section by means of ‘__attribute__((progmem))’
So, maybe try changing
char fiveLetterWords PROGMEM = “ALII...
const char fiveLetterWords PROGMEM = “ALII
The current version of the Alpha Clock Five software already has this change made — it was required by a change in the Arduino software. If you run into other difficulties, you might want to compare to the “official” source code, to see if those issues are addressed in it.