Here are official resources with installation manuals from all CAs we work with. Those manuals will help to Install SSL certificate to most traditional systems/platforms, generate CSR/KEY code on a server. Try use Search Engines like Google.com with keywords like "Install SSL to IIS server", or "Nginx SSL installation."
Resources
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Sectigo (Comodo)
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DigiCert (RapidSSL, Thawte, Symantec, GeoTrust)