Once in the navigation, you can choose between many different styles of menus. Once you choose the navigation you would like, WIX will automatically include each of your pages within the navigation bar. To place on your page, just drag and drop. Once on your page, you can fix to the whichever size you would like. Big or small, it is up to you. Also remember to place within the header of the page, as the navigation will then show on each page of your site.
On WIX there is a wonderful SEO tool called SEO Wiz. It makes the basic steps of SEO even easier by offering you suggestions, such as keywords which relate to your website. Once you set your keywords the tool allows you to analyze the keywords. Have a mixture of short-tail and long-tail keywords, as long-tail keywords are easier to rank for. The tool then offers you an SEO plan, which will hopefully start to rank your website.