Partitioning allows you to create a segment on a single drive to separate programs from files or install a second operating system.
Notice how your drives are labeled C:, D:, and so forth? Those are partitions and they are sections of the physical drive. Each hard drive in use contains at least one partition and you can actually shrink this partition to create new ones from the extra space.
Here are the steps you need to take in order to partition a drive:
1. Make a full image backup of your entire drive if you haven't yet. There's a number of Windows backup software you can use for this.
2. Verify that you have enough free room on your existing partition to create a new one. There's tons of ways to clear up space such as getting rid of duplicate files. You can also move files to an external hard drive and just move them back once you're done with the partitioning.
3. Open the Windows partitioning tool by typing "partition" into the search bar then click on "Create and format hard disk partitions".
4. Shrink the existing partition. Right-click the partition and select Shrink Volume. You're going to have to wait a bit. Eventually, the dialog box will ask how much you want the partition shrunk. The default number will be automatically set to the maximum space available.
If Disk Management is allowing you to shrink the partition to the size you want, enter the right size, click on "Shrink", and just follow the prompts.
If it doesn't allow you, you should use a third-party tool instead. Try out EASEUS Master Free-- it's very easy to use, too!
5. Create your new partition. Once the resizing is done, right-click the physical drive's unallocated space and select "Simple New Volume". Just follow the wizard from there!
And there you have it! Congratulations on doing your first partition. Now have fun with it!