freebsd installation on oracle virtual box

You can Download the oracle virtual box for free

https://www.virtualbox.org/wiki/Downloads

then you get the freebsd disk file for the virtual box
https://www.freebsd.org/where.html

unzip the .xz file with the following command

gunzip FreeBSD.vhd.xz

After installing the disk and launch the freebsd, use root without password to login.

Most likely, you are behind a router with dhcp server.

Use the following command to configure your network:

dhclient em0