Typically, a Certificate Signing Request (or CSR) code is generated upon your request by your hosting company for the website you want to secure with an SSL certificate.

However, you may generate a CSR code yourself (or your hosting company may advise you to do so). In which case, select your web server from the list below and follow the instructions.

If you do not see your server type listed above, click on this link for further instructions on CSR generation provided by Comodo CA.
  

If you are activating a Multi-domain certificate, and your server does not allow you to generate a CSR for multiple common names, activate your certificate using just one common name. You will be able to add all required SANs through your account during the activation process.