Subtitle Defining Question – Desperate!

I added the correct code to my header.php page in order to add a subtitle. However, I do not know what or where to insert code to define the added subtitle. Can someone please tell me what to insert and where? Thank you soooooo much in advance. Smiles.

http://www.neospyce.com/blog

Here is the stylesheet:

http://neospyce.com/blog/wp-content/themes/coffee/style.css