You can additionally check the SSL installation instructions provided by Sectigo Certification Authority here.
If you host your domain name with NiceNic, simply provide us with your certificate and we'll be happy to install it for you.
Please note that on all NiceNic Shared Hosting servers, a special NiceNic SSL plugin installs a 1-year free PositiveSSL certificate automatically on the newly added subdomain or add-on. It works the same way for the main domain in the newly purchased hosting account. The plugin can also be used for manual installation (in a few clicks) of PositiveSSL and EssentialSSL certificates. You can find more details on the free 1 year SSL offer in this article, and here's your reference guide on the NiceNic SSL plugin.
A dedicated IP address is required to install an SSL certificate. However, you may install your SSL certificate on a shared IP address using the Server Name Indication (SNI) protocol extension available in your cPanel. You can learn more about the differences between a dedicated IP and SNI technology in this article.
Keep in mind that the SNI technology is available on all NiceNic hosting servers. When contacting our support team with an SSL installation request, please specify whether you wish to order a dedicated IP address or have your SSL installed on a server's shared IP.