How to add/edit bridged adpater?

[wyx2000]

I have a VB on SunOS 5.11, I am trying to get one VM to connect to Internet. I have several VMs installed by someone, and when I check their network setting, I see all use "bridged network" and the name of each are "A", "B", "C".
I think those bridged adpater "A", "B", "C" were added somewhere, since I can pick them from the dropdown, but I have no idea where to add/edit them?
Also, I add a new VM "D", since there is no bridged adapter "D", I shutdown VM "A", and set adapter "A" to use on VM "D", but it cannot connect right, so it seems the adapter is one for one? I don't get how it works.

[noteirak]

These adapaters are in your host directly. Virtualbox only use them if they have the network filter, but they must have been created in the host, outside of Virtualbox, before anything.