Click on the flag to make it snow.
This project is from the book "Coding Projects in Scratch", by Jon Woodcock. (Page 144, 'Virtual Snow"). It teaches you how to use the Stamp block (one of the Pen Blocks). The Scratch Team made the Pen Category an extension. To get the stamp block and the rest of the pen blocks, you need to click the bottom left of the screen where it has 2 Scratch blocks and a plus symbol. Then click "Pen". Next I want to learn how to use the pen to leave trails behind a moving sprite.