Enter values for the various variables used in drawing the fractal tree when prompted. Press T to reset after your tree is drawn.
Got bored, so I ported my Snap! project Symetree over to Scratch 2.0, and it worked like a charm, so evidently Scratch can now... rival a quarter of the capabilities of its extensions, perhaps? At any rate, all I can say is to experiment with values. You'll end up with some pretty ridiculous trees at first. If it helps, the tree used in the logo has the parameters depth: 6, size: 60, leftangle: 15, rightangle: 15, leftsize: 0.96, rightsize: 0.96.