Add a border in tpl Files

Hi,

I'm currently creating a skin with a theme for League of Legend always as base a skin of Adante (yes again :p)

Now i would like if that's possible to add a border behind the container in the template files

Like this:
http://img191.imageshack.us/img191/9...nstitreltd.png

And like i don't know anything about the language used in those files, can you give me the command pleaaase :)