Just one operating system on C: is fine. You format the new partition if it hasn't been done already, that's about it. Remember, when transferring files from one location to another always use Copy and Paste. Once you confirm the transfer, you can delete the originals if desired. Cut and paste is dangerous to do if you get a blue screen, freeze-up, reboot etc.
I like to copy paste small chunks of data rather than whole partitions also. Basically a few gigs at a time.