PiDrive 1TB Foundation microSD boots straight to BerryBoot menu editor

When I plug everything in ( RPI 3, PiDrive Foundation 1TB) and power up with WD’s 4GB special microSD installed it takes me straight to the BerrryBoot menu editor. I know the PiDrive will require formatting and I have read everything I can find about the PiDrive. My RPI works fine with the original noobs/Rasbian card installed. I have double checked that I have all the connectors plugged in properly.
The system seems to recognise the WD microSD card ( I have the message Disk: 3238 MB available at the foot of the menu editor screen). The light on the HDD is permanently on.
I don’t know how to proceed to get my PiDrive recognised and formatted etc.
Anyone got any ideas, please?
Thank you