You'd have to manually craft the OpenVPN server settings to match your server config. You don't have to import the full CA unless you want to manage the keys on pfSense, but if you do want to import it all, see https://doc.pfsense.org/index.php/Using_EasyRSA_Certificates_in_2.x
If you just want to run the server on pfSense, you need only import the CA Cert and server cert.