im new to whonix and have a question

i have a mullvad sub and can i install in workstation (whonix)?

is it safe to use?

does it help anomity or does not help?

Unnecessary and possibly dangerous, it does not increase anonymity. You can try sys-net > sys-firewall > sys-vpn > sys-whonix – if you want to use a VPN.

As per:
Mullvad on Qubes OS 4 (Mullvad help)

Understand the difference between a VPN and Tor:
Whonix ™ versus VPNs (Whonix wiki)

If sys-vpn is running Fedora as a template I highly encourage disabling systemd-resolved in those templates. This is default for the Debian templates and fires up less networking resources also.

systemctl disable systemd-resolved
systemctl enable NetworkManager