Solved!
In case anyone else has this question, what worked for me was this:
(In case it matters, I did all this in Chrome.)
1. Set up desired username/password on tiddlyspot
4. Enter your username/pw in ControlPanel>Saving>Tiddlyspot
5. Save changes. Now you should have the alpha version in your tiddlyspot.
6. Go to Cardo.wiki and Download Cardo. Open it in Chrome.
7. Once again, enter your credentials under ControlPanel, and
8. Save changes.