Meta keywords are not a ranking factor for SEO anymore, speaking of Google's algorithms. If you can, you can add them by using simple HTML tags, or if it is difficult for you, by using Yoast Wordpress plugin, but I don't recommend doing this.
Skip the meta keywords, pay attention that you have your main keyword in the pretty url of your site, page title, H1, and variations of the word in H2 or H3, keyword density of at least 1% in paragraph text, and try to put the keyword as close as possible to the begging of the first paragraph on the page, so the text immediately clears the subject of the page. Then optimize you photos by putting keyword in their names, captions and alt text. Also, write a good, descriptive, meta description, up to 150 characters, containing keyword, and call to action, and you are done.
With these ones done right, you've done a great job on on-page SEO optimization, no meta keywords needed.
Btw, I cannot see your site, is it a regular presentation or e-commerce site?
Željko Janković, Digital Marketing Specialist