Netlify allows customers to install their own SSL certificates, providing an alternative to the free 1-click SSL option offered by LetsEncrypt. To do so, users must log in to their Netlify account, select their site, and click on the "SSL" tab. They will then be prompted to provide their PEM-formatted certificate, private key, and intermediate certificate chains. It's worth noting that installing a wildcard certificate can limit access to subdomains for other users on the same admin account. Once all fields are filled in, the user can click "Install Your Certificate" to secure their site.