you can start on page optimization for your website keywords, start link building, & there are many other factors in seo as well.
Do you really wanna know how to do it.. Then Start reading Blogs that has tips on HOW? you have to start with the basics and then later on you proceed with the complex things.. I will share you a link as a simple guide... Actually Google has a blog about it... Google's Guide and there's one I have found also : Guide to SEO