You have now learned six notes on the first two strings. When changing between tow strings use minimal movement with the right hand fingers. Practice the following exercise until you can feel a smooth transition between both strings.
As you learn more notes you will be able to develop a repertoire of well known songs. The following exercise is a simple variation of a popular melody that can be played with knowing only a small number of notes. Chord symbols have been included so try creating a suitable rhythm pattern to accompany the melody.