Once you have mastered enough chords to accompany most of the popular songs, you may want to add some melody. Essentially, this needs a bit different approach as you need to pluck bass, melody and chords at the same time. I’d suggest you start with exploring the common chord shapes also a bit higher on the neck than just the first position.

Here is an easy example that I have done on the Procol Harum’s hit A Whiter Shade of Pale. Playing it from the tab may take you to actually playing the piece but if you wish to create similar arrangements you should learn the standard notation.