My question is, where do I put the "font.h" file of letters, numbers, symbols. I thought that I could paste them into a .txt file and then put them in -
You copy & paste the font data from Nick's page into a text editor and save the file as font.h (not font.h.txt) into the same folder as the sketch file. You will probably need to close the IDE and open it again so it pick up the new file and adds it as a TAB to the IDE editor.