Hey Ted;
First make sure that your Win8 machine is in the same workgroup as the other machines on the network (host machine as well as others).
Set the network adapter setting from within the settings menu in VirtualBox to "Bridge Adapter" make sure that the proper adapter is selected below that (should be auto populated, but check to make sure in case you have more than one).
Determine in advance the IP addressing schema that your existing network is using... I will assume that you are using the private reserved class C, network of 192.168.1.0 through 192.168.1.255 with a subnet mask of 255.255.255.0 and a default gateway address of 192.168.1.1 You will need to have this information available when configuring the virtual adapter...