Install on HD

I install BSD on a usb stick using an Asus VivoBook laptop with an Ubuntu as OS. It works well but when I tryed to install NomadBSD on the HD a message appred:
Fatal error
/usr/libexec/nomadbsd-install commit returned with error code 1:
“gpart: geom ‘nvd0’: File exists
nomadbsd-install : couldn’t create GPT partition scheme”

I guess this because linux has already on HD and if I want to replace it I have to format the disk first or not?

By installing NomadBSD on HDD (SSD) I do the way for noobs.
I use two usb Sticks. On the one is the nomad.img, on the other is a live Linux Iso including the gnome-disk-utility. So I start the Computer with the linux live iso. Then I put in the second usb Stick with the nomad.img. Then I start the Disks GUI, choosing the HDD (SSD) click on “restore Image” and choose the nomad.img. Then I shutdown the Computer, put out the usb Sticks. After rebooting NomadBSD is installing itself automatically from the HDD (SDD).

Thank you, but I have got a version of Ubuntu already installed on the internal SDD. I already installed NomadBSD on a external USB SDD , add the new device on the BIOS boot and it works even thought I preferred having just one OS on my laptop.