What you have to do is put the folders/files you want to store on OneDrive in the OneDrive folder you see in File Explorer (place folders name as you will in the OneDrive folder for whatever type of organization that appeals to you)...that's uploading them to OneDrive. Once that's done, I go into the MUI OneDrive app, swipe in from the right, select Settings then Options and turn on the switch there that will make all OneDrive files available both online & offline. That will keep a folder/file copy on OneDrive and on your computer...that way if you don't have internet access you can still access your data...but setting it up the way I have mine still uses the same storage space on your computer as it did before you uploaded everything to OneDrive...i.e. it keeps a full copy on your computer and OneDrive.
Alternately, you can simply keep that switch I mentioned above to OFF and the folders/files will reside on OneDrive but NOT on your computer...you save space on your computer but need an internet connection to access your stuff. If you chose to have your stuff available for both online & offline like I do, then any changes you make to any of those folders/files will be updated immediately (well, depending on the size of the file, seconds to minutes).
With some of my programs, I set them in the options or preferences section of my program to locate my user files for that program to OneDrive under the appropriate folder I've placed there so that whatever work I do is updated automatically and directly and also is available on any other device I choose to use. OneDrive will continue to sync that data as well with my computer.
Hopefully this will help some.