Windows uses the concept of "drive letters" to identify storage devices attached to your PC. While quite unlike the filesystem mount model of Unix-based systems, it's an approach which has withstood the decades since the MS-DOS days.
Windows is almost always installed to the "C" drive. It's not generally advisable to change this, as letters other than "C" can break software which depends on this mounting. You're free to customise the letters assigned to other devices, such as secondary hard drives and USB sticks.
Open Disk Management by searching for
diskmgmt.msc in the Start menu. In the window which appears, find the partition you'd like to change the drive letter for. You'll see its current letter displayed after its name.
Right-click the partition and click "Change drive letter and paths." Select the drive letter which is displayed in the list. Click the "Change" button.
You can choose a new drive letter from the dropdown menu next to "Assign the following drive letter." Select a new letter and press "OK" on both the open popup windows. Windows will unmount the drive and then remount it with the new letter. The new letter will now persist for that drive.
If you want to do without drive letters, you can optionally mount devices into folders on NTFS filesystems. This is more akin to the Unix approach to storage mounts.
Back in the "Change Drive Letter or Path" prompt, click "Add" and then "Mount in the following empty NTFS folder". You'll need to browse to a folder to use. You'll then be able to access the contents of your device by navigating to the folder in File Explorer.