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.
On the client side, Ubuntu comes with the SSH client already installed. You can’t see it, because it’s not a GUI application. For the server (the remote computer you wish to SSH into), you’ll need to install the SSH server software. (Read the rest at Freedom Penguin)