No need to optimize Iframe becasue it will not help your website or content to improve SERPs as well as not badly affect your website's SEO ranking.

Still if you think it will help at some level or have requirement to implement it then follow below sytanx while applying it on the website:

Read more about it in detail at www.visibilitymagazine.com/how-do-iframes-affect-your-seo

[DELETED]