You are not going to find instruction in Thunderbird help on how to generate a app password on your mail providers server. Each mail provider does it just a little differently.

I suggest you try searching app password and your mail providers name.

Thanks Matt. I thought that the password was Application specific (as it's name implies) and not related to my mail.me.com log-in!

it is application specific. but specifically allocated at the other end of the authorization equation.