How do I merge these 2 storage partitions?

[inck243]

I wanted to create a partition on the MacOS drive to use as extra storage in windows. When I created a 900GB partition, it took the smaller space and made that into a new partition which is the opposite of what i wanted. I tried again and this time changed the name so it would make a new partition instead of keeping the larger chunk for the OS X volume. Now I have 2 exFat partitions named Storage.

I'd like these to merge into one partition. What steps are required to do this in El Cap? Thanks