Is there anything I should be aware of before setting up a virtual network?

I've never done this before and tbh networks etc is something I'm not familiar with I'm going to setup a virtual network via this method

http://m.wikihow.com/Create-a-Virtual-Networks-by-Using-VMware-Workstation

Anything I should know before doing this? Possibly in terms of security? Im considering splitting it up an running the 4 vms on two separate machines if possible..