This is scarily addictive. :ermm:
Put the little circle on the scissors on the edge of the paper (the circle will go green) and click - then move the scissors to somewhere else on the paper to make a cut. Note that you can't start a cut in the middle of the paper.
Have fun! I've made loads now, you can save them all and add them to the thousands and thousands already there! And you can apparently buy stamps with your snowflake on...
Here's one of mine: