Apparently the only person on this thread who actually has a harpolute is the OP, richardw, who posted 17 years ago.

But supposing somebody comes along who has one today, I suggest that you tune it in C (see OP), get some metal fingerpicks, and sound out songs in C on the strings. You might want to get one or two picks for the left hand and throw in a little harmony.

I have seen a toy instrument like this, where you plucked at one string at a time with a triangular plastic pick, but that seems like a limited approach.