Styling wp pages with css

When creating a page on wordpress you have the option to use the html tab but how do I style it with css? Can I link it to the already exsisting css style sheet the whole theme is already linked to and how do i do that?

Many thanks

You can make it (styling wp pages with css) in many ways. It depends.
You can use your html tab in that page (write all necessary html code) and than style it in main css file (you may need to use any php allowing plugin for that).
You can also make special wordpress template page for that, use it in page admin area and also style it in main css.