When you first install Foobar2000, you’ll need to set up the Media Library. The library function monitors your music folders and allows you to access and manage your audio files. The better the accuracy of the filenames and the metadata, the more accurate the library catalog functions will work. You only need to add the main top folder. You can also add additional main folders in other locations.

File > Preferences > Media Library > Music Folders > Add…

Adding audio files to your Music folder will automatically be included into your library. You can also directly point Foobar2000 to new folders or files via the Files menu.