The default username is admin and there is no password . You will be prompted to set one immediately upon the first login.
The specific compilation number of that firmware release out.kvm.qcow2: The disk image format (QCOW2) used by KVM Where to Download fgtvm64kvmv723fbuild1262fortinetoutkvmqcow2 download link
Designed for Kernel-based Virtual Machine hypervisors (like Proxmox, QEMU, or Nutanix AHV) 723: Version 7.2.3 The default username is admin and there is no password
Ensure you allocate at least 2GB of RAM and 1 vCPU for the initial boot. fgtvm64kvmv723fbuild1262fortinetoutkvmqcow2 download link