|If by "host machine" you mean doing NAT for your network, I would recommend buying, and using, a SOHO Router instead. With servers you always want to offload any services you possibly can so they can spend their time and energy on their main purpose.|
Nobody here is going to give you "step-by-step" instructions on anything. We're here to help, not do the work for you. This applies most especially if you're in school working on homework.
If this is work related then you should give some thought to paying us or hiring a qualified consultant if you don't know how to configure a NIC (or NIC's as the case may be).
My suggestion above is valid, and simple. Buy a SOHO Router and let it do NAT. Then if you have dual NIC's you can connect one to your LAN (and therefore the internet too) and the other to your test environment.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.