I followed the guide up to "mysqladmin -u -p create mydb" (mydatabase)

There I receive following error:
CREATE DATABASE failed; error: 'Access denied for user: '@localhost' to database 'mydb''

I am wondering why it does to say 'root@localhost' anyway I did repeated the process and got the same thing again.

I am running a new install of Debian
I am a newbie to Linux but not to computing. Started up in the 80s on a commodore 64 moved to Amiga 500 then to Amiga 1200 and finally 1993 to IBM. (Still own all my Commodore machines)