The Mac and Windows window has three parts. The sidebar on the left holds your library or a playlist and its song list. The middle shows the current song. The player controls sit on the right, or along the bottom when minimized.

 

Hide the left and right sides independently: click the button for each one, use the View menu, or press its key command. On Windows the sidebar buttons are at the top right. Neither side can be hidden while you are editing a song, because the Editor panel takes the right-hand side.

 

To change the column widths, hover between the library and the song list, or between the song list and the chart, and drag sideways.

 

For the full guide, see Play a song on the iReal Pro website.