This exercise is from the Core Skills exercise on Muting.
In this exercise we use the thumb to mute the low 3 strings. Similar to the last exercise we play the melody line by fretting notes along the G string. Whilst playing these notes, use the finger to also mute the adjacent 2 high strings. Notice as well that the actual melody notes are often muted too for rhythmic effect.
By playing fetted notes along with muted strings we add that extra bit of bite into each note. The 'click' of the muted strings being hit adds a bit of edge to the fretted note.
This is also a good exercise for giving your little finger a proper muting workout. Like all funk tunes, rhythm is essential. Work on keeping your strumming consistent. Listen to where the notes are played and where they are muted. When you are familiar with the tune you will find it easier to perform it.
The notes played are:
x x F# x x F x x D# x x F x x F# (hold this note for an extra beat then repeat)
x = muted strike
NB. The tune starts out without the first 2 muted strikes before the first F# note. After that, the above pattern applies every time.