Import and use google webfont

Question

For a project, I have to use many style off a font. Here is the link of the google font

Here is my css import

@import url(http://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,700italic,300,400,700);

What I would like to know is how can I define the font-family to display for example the "Open Sans Light 300 Italic"

Thanks