Keywords and the importance of them are something that you will see pop up time and time again when looking at SEO. The impact they have on your whole strategy and how successful it will be cannot be overlooked. They also cannot be done once and forgotten about, the most important part of keywords themselves is relevancy, to be relevant they have to be up to date.
When you implement new keywords, keep an eye on how they perform and start to learn the phrases people are searching for and which to use.
They are also important to give Google an insight to the topic of a page. The more relevant your topic to the search query the higher chance you have of ranking above a website that is lacking in rich keyword relevant content.
Make sure that your page copy is relevant, and do not neglect to include keywords in meta titles, descriptions, headers and featured snippets. However, make sure that you do not overwhelm your user. Improving your page titles can make them more relevant to the search term and therefore make them more appealing to click, giving you higher click through rates. This is especially important for when pages are not ranking or getting as many clicks as they should be. You can look at what pages are performing or are not performing well through your Analytics.