How can I partition a 6TB HDD in Win 10?

I have a new system running under Win 10 on which I want to use an SSD as the boot drive with all my s/w and a WD 6TB Black HDD for my data. However, when I format the 6TB drive it shows up as two unallocated segments, one of 2048.00 GB and the other with 3541.03 GB. The smaller one is available for a simple partition under Win 10 Disk Management, but actions for the larger one are all greyed out. When I make a simple partition in the smaller one the option to extend the partition is greyed out. Does anyone know the secret to using the full 6TB under Windows 10?

right click on your disk in disk management on 5889.xx GB and convert it to GPT disk.