At the beginning!
In all seriousness, begin the simulation by watching the sweet walk-through video. You'll have the chance to watch the video after you have paid for the simulation and clicked, "Go to Mimic Pro". It will immensely help you down the road if you take the time to watch it.
After the video, click "Get Started" which will take you to the Scenario page. This page will give you the lowdown on Kent's Camera as well as previous data that you can use to decide how to proceed. Then continue through each decision listed on the left side of the page. Once you complete a decision it will see a check-mark next to the decision.