I have checked my website using this SEO tool and the results report 2 issues:
Test your site for potential URL canonicalization issues. Canonicalization describes how a site can use slightly different URLs for the same page - for example: if www.mydomain.com and http://mydomain.com displays to the same page but do not resolve to the same URL. If this happens, search engines may be unsure as to which URL is the correct one to index. Learn more about canonicalization issues.
www.mydomain.com and mydomain.com should resolve to the same URL, but currently do not.
Your site's IP xxx.xxx.xx.xxx does not redirect to your site's domain name. This could cause duplicate content problems if a search engine indexes your site under both its IP and domain name. Consider using a 301 re-write rule in your .htaccess file so that your site's IP points to your domain name. Read more about canonical URL issues.
How can I configure my website to solve the 2 issues above? My website uses a Window server (ASP.net). I want to optimize for SEO, but first I must solve this.