Allow me to let you in on a little secret - I have never used PuTTY or PuTTYGen. All of my key generation has always been done in the Linux command line. Lucky for you my familiarity with the latter is going to help you overcome the former. First, allow me to acknowledge that most documentation is convoluted. Despite interesting details being presented, often it comes across as a wall of text to Linux newcomers or those simply new to certain aspects of Linux.