I'm not entirely clear on what you're asking. Are you trying to find out how to -display- lyrics or how to -obtain- lyrics?`
To display, you need to open the panel configuration window (little 'box' icon next to the search box) and drag the lyrics element to any section that shows a red bar.
To obtain lyrics from outside sources, MB has a built-in feature which can be configured in Preferences > Tags (2) > auto-tagging > lyrics.
In addition, there is a plugin called 'Lyrics Reloaded' which can be installed and then configured in the same area. This plugin is basically unsupported at this point but if you work your way through the thread you'll find some additions/fixes to the provider list.
Thank you! Is there a way to make the client download automatically floating lyrics, or lyrics that highlight the parts of the lyrics that are sung at the moment?