Start slowly. Use an online tutorial such as the one found at w3schools.com/Css. Learn just a handful of useful CSS properties and selectors. Then write some simple HTML and apply the simple CSS you have learned. Don't try for a moon shoot start with simple things. Like changing the color of a single line of text, or learn how to apply simple formatting to an HTML list. Remember the internet is an amazing source of examples to help you understand CSS.
