You can configure a private network between the two hosts on an interface of your choosing. Alternatively, I suppose if you have a dhcp server on your host machines network that you can bind guests interfaces to, they'll be able to communicate on your own subnet but this is probably not advisable seeing as what you really want is a lab.
Check the
documentation on virtual networking for details on the three modes available to you.
To transfer files between your hosts you can use a number of application protocols. If you are just looking to get shared files from your host onto your guests, then look at the "shared folders" functionality from the virtualbox
guest additions packages, again, referring to the documentation.
the `uname -n` command will show you the hosts current name.
