Go to VirtualBox preferences, select Nat networks under network segment and create new Nat network.
Then go to virtual machine settings on the adapter one tab under network segment.
Attach the virtual machine to Nat network and choose a Nat network you created.
So now let's provide connectivity between your virtual machines.
So the way I'm going to do this, I will include all of my virtual machines in a Nat network.
I'm first going to start with Carly, so I'll choose it.
Click settings.
Go to network settings.
Change Nat to Nat network.
Right.
And click okay.
Now do the same thing for the other virtual machines quickly.