By default, apps downloaded from the Windows Store are automatically installed at the root of your system drive (in C:\Program Files\WindowsApps). However, if you are running out of space on your primary drive, Windows 10 gives you the ability to move your apps to another drive.
Move Windows Store Apps to Another Drive
Go to Start > Settings > System > App & features and launch a search by typing the name of the desired app into the Type an app name field. Once found, select the app from the list and click on the Move button:
Select the destination drive and click Move:
N.B. If the Move button is grayed-out, it simply means the app can't be moved around.