Select Compute -> Virtual machines from the left sidebar
Select the virtual machine which you wish to attach the assigned shared disk to
Select Disks -> Shared disks from the navbar
Click the name of the shared disk you wish to attach
Click Attach to virtual machine in the Actions sidebar
The shared disk will now be attached and can be used within your virtual machine.
Detach shared disk from a virtual machine
Select Compute -> Virtual machines from the left sidebar
Select the virtual machine which you wish to detach the assigned shared disk from
Select Disks -> Shared disks from the navbar
Click the name of the shared disk you wish to detach
Click Detach from virtual machine in the Actions sidebar
The shared disk will now be detached from the virtual machine.
Do you wish to prevent the disk being attaching again in future? If you wish to ensure this disk can no longer be attached you must also unassign it from the virtual machine.