The y axis ("Y to the sky!") shows how emotional the film is at that moment. It goes from negative emotion at the bottom to positive emotion at the top.
The x axis ("X is a cross!") shows time passing in the film. You can either choose to stop the film at key points and mark the level of emotion at that point or stop the film every thirty seconds or so.
When you have decided how negative or positive the feel of the film is at these points and popped dots or little crosses on the graph, join them up using a ruler and label the line with what is happening. I wonder what your graph will look like. Will it look like a mountain, a pit or a bumpy road? Will all your graphs look exactly the same? If you are able to, post a photo to the blog so we can compare.