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.
The basics of SEO are very important to comply with. They help search engines understand your website and what it is about. Using algorithms search engines will then rank your site appropriately to specific searches. Ideally you want your site to be on the first page of a search, which can be very hard. Generally the basics of SEO does not achieve first page ranking as it requires a bit of work and effort to do so.