VirtualBox: copy and paste between host and guest OS

To enable or disable the copy-and-paste between the host OS and the guest OS:

1. Select the guest virtual machine.
2. Click on the Settings button or from menu Machine|Settings...
3. In Settings, click on General.
4. Click on the Advanced tab.
5. Click on the option of Shared Clipboard and choose Bidirectional.
6. Restart the guest VM.