Hi Rajkiran_M
I am Dave, I will help you with this.
Windows has very little partitioning capability, it can only extend into a space that is directly to the right of the C drive.
1
If the space you have created is not directly to the right of the C drive, you will need to use a 3rd party partitioning tool to extend that partition, the free version of AOMEI Partition Assistant is fully featured and will easily extend your C drive partition.
2
If the space is directly to the right of the C drive partition, please provide a screenshot of your Disk Management window.