You should do the following:
- In the SSL Certificate field:
Paste the contents of the certificate issued to your domain. In windows you can usually verify this by simply double clicking (or opening) the .crt file. A window will pop-up with information about the certificate. Just check under "Issued to:" and make sure its issued to your domain.
- In the SSL Key field
Paste the contents of the key that was created during the generation of the csr. It usually begins with -----BEGIN RSA PRIVATE KEY-----
- In the SSL Certificate Authority/Intermediate
Paste the contents of the CA bundle certificate you received from your CA. That is the certificate without your domain name under "Issued to:" as explained in step 1.
Hope this helps someone. You can also read https://support.dnsimple.com/articles/what-is-ssl-certificate-chain/ to understand certificate chains.