I presume you mean the entire profile, not just one account. If you're using ver 102, the process is easy. Click tools>export on desktop pc and tools>import on thinkpad.

Hi David, thanks for this quick reply with a simple solution. BUT here's the thing. I have two Gmail email addresses. One is already routed through TBird on my ThinkPad. I simply want to add the other. Is there a simple way to do that without exporting something much bigger? I'm not very savvy and worried about messing with the Profile stuff which I've never really understood. Toni (my moniker when seeking help on most apps is "Dumb Old Lady"

File menu or appmenu (≡) > New > Existing mail account.

Follow Matt's suggestion. Thunderbird knows the details of Gmail, so you just need to identify that information and email id. Do NOT enter a password. Google will prompt to verify your email id and then will authenticate the account. Entering name and email address is probably all you need.