When you import your certificate on the Qlik Sense server, it will require the private key and you will want to use a server certificate to create the trust between IIS and the Qlik Sense server. I recommend importing the certificate to the Local Machine\Personal certificate store.
Depending on the CA that created the cert, you may have to add the root certificate from that CA to the Trusted Root Certificate Authorities Store under Local Machine as well.
I think a Cert Request can be created by IIS, but it has to be able to talk to existing CA in order to create a cert from that request. You can create a self-signed cert on the IIS server (I'm sure you know that), but that's not going to give you what you want I think.
I do not believe there is a way to take the CSR and ask the Qlik Sense server to complete the request because their is no CA on the Qlik Sense server to process it.
Is there a reason you don't export certs from the QMC supplying the IIS machine name in the dialog to have a server cert created for that system that will be trusted back to the Qlik Sense server?
Don't know if this is helpful, but if you provide me some more information I hope I can answer your question completely.