When you configure your source and you hit OK it should have asked you if you wanted to scan for content or something to that effect. That would be updating the library and should have added in your content. Typically you would see the progress in the top right of Kodi’s UI if your not actively playing video. From that point forward when you add content you would go into a library view (movies, TV, Audio) and then go to the side/slide out menu (depending on skin and view normally you would bring it up by navigating all the way left or up) and tell it to update the library. Note that Movies and series are updated at the same time but audio is separate and would need to be told to update on its own.
There are options you can enable to update the library on startup or on a timer schedule. I don’t recommend doing either. If your using the OSMC remote there is a shortcut to updating the video library by holding down the play button when you are on the home screen.