Different css style in only one page

Hi everybody

Iḿ just trying to create a welcome page with a slightly different style in my site. The template I’m using is twenty-eleven.

I’ve tried it creating a new-page.php template but doesn’t work… how can I change things in it if there is no style information in it? Im just wondering if I should create a new css sheet… any idea? I’m sorry Iḿ new in changing this things.

thanks a lot in advance

Koxme