Assignt automatically two categories by author

I'm looking for a way to automatically assign two categories each time an author makes a blog post:

1. General category (will always be the same for all authors).
2. Author category, with de same exact name as the author.

For example, assign to a new blog post from user Bilbo the generic category 'TLOFT' and the author tag 'Bilbo'.

I'm sure this won't be really complicated, but I'm just starting and I get lost when away from html, css and minimum java...

Hope anybody can help! Thanks in advance!

Edit -- This is the structure: