The virtual machine contains out-of-the-box support for the AMD and Digilent programming cables. If further support is needed, you need to pass through the USB cable to the guest to make it available to the Impact and ChipScope™ tools.
To configure the machine to capture USB devices while the machine is not running you can follow the instructions in the Oracle VirtualBox documentation: 3.10. USB support. If the machine is running, the previous instructions will work, or you can use the menu in the status bar of the VM to attach USB devices through to the guest.
Right-click the USB icon located in the of the VirtualBox window in the following figure.
Then click the device you would like the guest to have access to. This operation will transfer the device to the Virtual Machine. Keep in mind that the guest will need drivers for the device in some cases. Please follow the cable manufacturer's instructions for installing the Linux drivers.