Follow the post OpenVPN Server [Link] and create a user for pfSense as a VPN client.
ADD CERTIFICATE AUTHORITY (CA)
ADD CERTIFICATE
CLIENT CONFIGURATION
ASSIGN WAN VPN INTERFACE
FIREWALL RULES
Read Also
Performance OpenVPN vs WireGuard [Link]
Setting Up WireGuard VPN [Link]
OpenVPN Server + Monitoring [Link]
GRE VPN Tunnel on Cisco [Link]