Step by step instructions - Drumhat

Hello, I am a complete pi novice. We bought my son a drum hat for his pi3 and have plugged it in and have tried to follow installation instructions but all seem to assume some prior knowledge. Can anyone point us in the direction of some really simple instructions? Every time we have tried following these instructions our pi throws up an error -

What is the error?..

And when do you get the error? Do you get the error during setup of when running examples?