Help with VirtualBox Guest Additions using OMV_1_Kralizec_x64 Appliance

As a recap, I've been trying to get the OMV_1_Kralizec_x64 appliance up and running inside the VirtualBox plugin. I am up and running, but my latest issue is Guest Additions.

The iso is in the virtual drive. When I click Settings => Install Guest Additions, I get a error message:

"Failed to update Guest Additions. The Guest Additions image will be mounted to provide a manual installation."

Details:
(0xFFFFFFFF80BB0009)
Guest Additions not installed or ready, aborting automatic update

Inside the guest OMV, under File Systems, the iso shows up as device /dev/sr0, not mounted.

Dont want to go TMI on you, so any help to get Guest Additions installed would be great.

Thank you. That was quick and easy. Having a lot more experience with VBox on the Windows side, I'm still picking up these nuances. So, for clarification, does the iso even need to stay in the virtual drive once the installation is complete?