Search engines are autonomous and choose what pages are shown in their results. They evaluate websites using crawlers (small "robots" that read websites and choose the most relevant out of thousands of pages).
Here are some quick tips which will help you optimize your website so it will land as close to the top as possible.
First of all, always keep your website active and up to date. High quality and well maintained websites do better in page rank.
Next, focus on keywords. Brainstorm and identify relevant keywords and keyphrases from all sections, categories, documents, headers, descriptions, tags, and even your domain name. These meta keywords can be inserted in the individual category and document settings. Just go to the category or document, hover over the yellow edit icon in the upper right-hand corner of the page, and select Settings. When entering the words and phrases, separate them with commas; this text is shown to browsers.
Finally, register your website with the search engines you would like it to appear in. You can do this through the search engine's website. If you would like to register with Google, for example, go to
https://www.google.com/webmasters/tools/submit-url.