It would be helpful if you upload a screenshot of your Disk Management.
Do you have some unallocated space when in Disk Management? Is this unallocated space on the left of this c: partition? In case it is not(not adjacent to c, you will need to extend the partition using some kind of a third party partition management tool.
Keep in mind that it is always a good idea to back up the data stored on the drive before that.