Issue
I need to generate a CSR in order to acquire a certificate.
Resolution
We have instruction on the process for acquiring an SSL certificate (for use with Heroku SSL or the SSL Endpoint addon) here: https://devcenter.heroku.com/articles/acquiring-an-ssl-certificate
As an alternative to buying and renewing your own certificates, Heroku customers can also take advantage of free SSL certificates (no CSR required) as part of the Automated Certificate Management feature https://devcenter.heroku.com/articles/automated-certificate-management