When you open the program, you immediately start in View Mode. This mode is intended to keep the operator from accidentally making changes to the Set List. Switch to Edit Mode by clicking on the View Mode toggle button to add files, move files, or delete files.
The easiest way to add songs to the set list is to partially type their name into the search and press Enter. This also clears the search entry so you can easily add the next song.
You can add files to the song list by clicking on "Add File" or simply dragging the file into the Current Set.
When you're in the presentation mode, you can use the mouse or the keyboard to navigate. To use the mouse, click on the slide you want to view in the contents window, then click on the file you want to view in the main window.