Every page on your website needs to be indexed well by Google. Don’t index any ‘none essential’ pages such as terms and conditions and privacy policy pages. These typically don’t need to show up in search results.

For your individual pages; add your target keyword phrase in title, content and alt tags. Aim for an article length >300 words in which you weave in your target phrase and any semantic variations.

You want quality over quantity, however Google is said to consistently rank higher content with over 1,200 words, so aim for in-depth, useful SEO copywriting and SEO optimised images. Try to get your target phrase appearing as early as possible in the first paragraph.

Take time to thoughtfully craft your titles and Meta descriptions for each page. These are your sales messages on Google search page results, designed to entice a searcher to click on your result rather than another. A carefully optimised Google search snippet is a driver of traffic to your website, so make each page unique.

Include internal links on each page. This cross-linking will help Google understand your site structure and also encourage visitors to dig deeper into your site, so lowering your ‘bounce rate’.

Keep your website visitor at the forefront of your goals. If they are happy then the search engines will be happy and reward you with higher ranking.

During this process, make sure any current content doesn’t lose its existing ranking. Create thorough 301 redirects or retain and don’t adjust any already high-ranking, high traffic content.

There are many factors that Google uses to rank your page over another; here is a useful resource by Moz to enlighten you further:
https://moz.com/blog/visual-guide-to-keyword-targeting-onpage-optimization