Welcome to the forum!
You could start by getting an SSL certificate:
If you’re using free hosting with your own domain or a subdomain, you’ll want to make your website work over HTTPS (SSL). Fortunately, InfinityFree provides all the tools you need to make it so. If you like videos better then text guides, scroll on down to the bottom of this guide.
This guide uses the control panel functions and the Free SSL Certificates tool provided by InfinityFree to get SSL up and running on your site.
But if Instagram still doesn’t allow you to add your website, I suggest you contact them. We won’t be able to help much because we don’t control Instagram’s standards.
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