Joomla and SQL

Hopeless beginner here.

I used the one-click install and followed instructions on the robot email. I think.

I got as far as the Joomla admin login, became confused about which u/p I should be using, went back to my cPanel to check, and now can’t get back to the admin logon.

If I try to get there via browser, I get “Database Error: Unable to connect to the database: Could not connect to MySQL”