Store/save password for digital ID signature

I'm hoping you can help me store/save my password for digital signatures so that I don't have to enter it each time. I've followed the directions I found on the web from Adobe. (Preferences>Signatures>More>Expand Digital lDs>Select Digital ID Files.) However, when I do this, thre is no Digital ID File on the right to select.

Given that, how can I store my password so I don't have to enter it each time? Any insight would be greatly appreciated.