After finding out what Search Engine Optimization (SEO) actually is, it's important to understand how it works.
Neutrally, we judge a website by the way it looks. The search engines on the other hand, judge a website by it's text.
When the robots and crawlers of the search engines go through your website, the only thing it can really understand is your text. If you have a nice photo/s on your website, the crawlers will only be able to see it, if you add "alt text" to the image (this video shows you how to add alt text to your images).
Now that you understand that the search engines only see the text of your website, all you need to do now is write the content for your web pages.
Okay... maybe you don't like writing or feel that you're not so good. Once your business grows you can hire a writer, but until then, visit websites like ArticleValley.com and ArticleCity.com that allow you to use other peoples articles on your website (always read the terms of use) and find articles on your topic.
Read through a few and then write your own unique article. Yes... you can just add the article as is to your website, but the problem with that is that search engines DO NOT like duplicate content.
If your website is filled with other peoples content... your website can be in danger of being Ignored by the search engines.... literally.