E-A-T stands for Expertise, Authoritativeness, Trustworthiness.
You need to be an expert in your field. Expertise means you need to show the skill of the creator for the Main Content or and mention it in your content. The good news is any site can show expertise if the content is truthful and useful for users.
You need to show that you are an authority or the authoritativeness of the creator for the main content. And you can get this from the expertise of your writers or yourself. If your page is a community or forum discussion, the quality of the conversation drives authority. Credentials are necessary, but so are personal experiences like reviews.
You need to show users they can trust the creator or company of the main content, itself and the website. Trustworthiness is especially important for eCommerce websites that ask users for their credit card information. Everything about your site should make users feel safe while they’re visiting. As a starting point, you should immediately implement an SSL certificate on your site as at least 70% of first page results are using SSL (It’s one of many of Googles scoring signals)
You need to eat to live. And so does your website content. A different kind of “eat,” but the idea is the same.
Google states that E-A-T is among the top 3 considerations for Page Quality. So if you haven’t been paying attention to E-A-T content before, you should start doing so. Immediately.