The same way as any other web application would be, via its address (name or ip). The fact its in a VM makes no difference to how you access.
So your first thing is to make sure your VM is properly connected to the rest of your network.
So you'll need to be checking/answering things like:
Can you see your router/modem from your VM?
Can you ping the host machine? Can the host ping the VM?
Most VM hosts automatically install the required networking stuff on the host (Windows probably bought up a driver install confirmation dialog when you first installed VirtualBox) to do this.