<httpProtocol>
<customHeaders>
<add name="X-Frame-Options" value="ALLOW" />
</customHeaders>
</httpProtocol>
I have added this in web.config file and want to allow site for x-frame from https://preview.codecanyon.net/
You may try with the below. Moreover, you can check here for more details.
<add name="X-Frame-Options" value="ALLOW-FROM http://xxx.xx" />