Hi Alan,
As Ian has mentioned (later in his reply), you need to be playing a chord with your left hand for the Strum to work.
Make sure your harmony/echo button is turned on. Then use Direct Access to go to it (press Direct Access and then the harmony/echo button).
Select the Strum type.
Then, while depressing a C chord on the left side (with or without the style playing), press just one right hand note and you will hear the C chord strum with the note you have just played. It will only strum once, so you need to be constantly pressing notes for it to continue strumming that chord.
Two nice things you can do with the strum when in the harmony/echo area -
1) Control the volume of the Strum.
2) Use the 'chord note only' feature.
If it is 'on', then it will only strum when you hit the notes of the chord you are playing (example C chord = C E G).
It will not strum when you play other notes besides the chord you are depressing with your left hand (example C chord -no Strum on D F A).
If it is 'off', then it will strum regardless of the note played.
If you only want to play (strum) chords with your right hand (not playing a melody), and only want to hit them once or twice per measure, then try the Echo at 4 speed (or 6, 8 or 12 for more 'strumming'). The Echo will speed up or down when you change the tempo, but it does not follow the chords that you play on your left hand.
For this method, if you play broken chords or a melody, of course you will then hear all the notes randomly echo and your 'strumming' will be lost.
Hope this helps...