One of the most powerful indicators of an authoritative website is fresh content. If your site is regularly updated, it sends a powerful signal to search engines that your site is active, that your business is active, and that the content on your site will be useful for search engine users.
So how do you keep your website fresh? One of the easiest ways is through blogging. If the term "blogging" intimidates you, consider simply calling your blog "news" and posting news stories from time to time.
While there's no magic number for how often you need to update your site by publishing a new article or blog post, best practice is to figure out how often you'll be able to add a story and to regularly do so at a pace that you can sustain.
If the pace you pick is to add a story once a month (about a 20 minute commitment once a month), a useful strategy is to set aside a block of time ASAP and write as many new stories as you can. If you write 10 today and only post one, you could publish another one every month for the next year and never run out of new content.
For content creation ideas, see the "Ideas" tab under the content section.