While trying to get Boot Camp set up on my MacBook Pro 15 inch Retina 2015 it asked me to partition my hard drive. Doing so I partitioned my 1 TB hard drive so that it dedicated 750 gb to mac and 250 gb to Boot Camp. However the Boot Camp set up was not successful and now my Mac's hard drive is only 750 GB big. With Boot Camp uninstalled it is still 750 GB. The 250 GB can not be added again on my Mac. Every time I try and add a partition to the "unallocated space" it does not work. I can't get my hard drive back to the full 1 tb. It looks something like this.
Someone please help me restore my Mac to its 1 TB hard drive. It would be very much appreciated.