Go to utilities click bootcamp follow the step by step instructions 

Format the partitioned drive first

Give the partition at least 40GBs

Make sure you have a valid copy of windows 

If you need more help here are a couple of videos with step by step instructions 



https://www.youtube.com/watch?v=ShdKIMA7gz0   How to Install windows 10

https://www.youtube.com/watch?v=X9w3sFsiaA0   Make a Bootable usb