Setting Up Target OSes and Kali Network Configuration?

Hey guys, so I want to install target OSes in Virtual Machines to practice, but all of the supposed pre-activated OSes still require me to give product key when I select the ISO from my Downloads folder for the Virtual Machine. Also, what network settings should I use for Kali Linux in VirtualBox? It appears that I can't connect to the internet when it's on the NAT setting. Thanks!