In the top left corner you can see "S". This means that your triangles will share a common side. If you click the "S", you will see other abbreviations. Go through each of these and explore a bit. What is the minimum information you think you need to prove triangles are similar?
You can drag the points in triangle ABC in order to change the triangle. You can also alter some of the points in triangle DEF.
Once you have examined all of these shortcuts, select the right arrow at the top of the screen to move to part 2 of the worksheet.