Need to change password for new computer

You do not need a password to use Thunderbird. Thunderbird is a mail client. The message that it requires is your email account password. You can reset your email account password via your email's web interface.

Understood. But it's my email account password that I don't remember. How do I reset that?

You must reset your password at your email provider's web site. Once you do that, you can update your saved password in Thunderbird at <Settings | Privacy & Security |Passwords | Saved Passwords>.

what is the web site for thunderbirds email provider?

what is the web site for thunderbirds email provider?

What's your email address? Thunderbird is not a email provider (yet). Your email address should indicate your email provider. Normally, you can reset your password under your email provider's web site (following their instructions).

Thanks, everyone. I was able to reset my password through my email provider, and this issue has been resolved.