The main premise of using Instagram for SEO is using hashtags, as you would use SEO keywords. You can also link to your website either in the photo or video's caption, or via the main Instagram page.
You also can link your Facebook and Twitter pages to your Instagram page, to further drive traffic to your website.
Samsung Mobile has a link to its Galaxy product page on its main Instagram header:
Also, you can embed your Instagram posts on your website. To do this via Instagram on a web browser: