HELP: Windows 7 Pro via Oracle VirtualBox on a Linode virtual server

In order to do some testing, we have created a Linode ubuntu 16.04 to install Oracle VirtualBox and then run Windows 7 Pro. We have successfully installed VirtualBox but when we run it we get an error: "Qt FATAL: QXcbConnection: Could not connect to display. Aborted (core dumped)". Obviously since this is a virtual server there is no display. We have been told that it is possible to get this working, but despite our efforts we have not been able to do it. THEREFORE, we are looking for someone who has done this and is able to provide us with simple instructions to make this work. We want to be able to run VirtualBox and then install Windows 7 Pro (SP1 and SP2) and then use it via a browser to do testing.