HSTS subdomain question

I’m using SEMRush to perform a site audit on a new project hosted with webflow. My preferred domain is https://www.abcd.com. I’m receiving an message error with SEMRush that my subdomains www.abcd.com and abdc.com don’t support HSTS. I’m okay routing traffic away from these domains…My question is, do I need to set it up? and where can I find instructions on doing so?


Here is my site Read-Only: LINK
(how to share your site Read-Only link)