Move the bucket with your finger, and try to copy the paintings in the examples. The more similar to the sample your painting is, the higher your score.
As you progress you will have access to new tools: more colors, different brush sizes, more than one brush, etc. You start with one color, but as you progress you will have access to more colors. In the last levels you will have access to different widths and styles of the acrylic paint drops.
Are you ready? Good luck!