The way to go ist using cloudinit to deploy a user/passwd or ssh-Key on first boot.
The steps I took are exactly like below:
Uploading qcow2 file to custom image upload section -> Select qcow2 file from custom images area tick send e-mail to me and entering scp password -> then it automatically redirects me to vnc console after installation.
In vnc console after installation first thing i see is vnc asking me for login username and password. There's no command line or anything.