Enabling Clipboard: VirtualBox Manager -> Settings -> General -> Advanced -> Shared Clipboard /Drag’n’Drop: bidirectional
Installing Guests Additions:
Enabling optical drive: VirtualBox Manager -> Settings -> Storage -> Controller Sata -> Adds optical Drive -> Leave Empty
Copy Guest Additions to the available folder on Mac: Finder -> Applications -> VirtualBox right click, Show Package Content -> Contents -> MacOS: copy VBoxGuestAdditions.iso somewhere to the folder