This article will help you:
Once you've defined your experiment goals, set up your variants, and allocated your traffic, launching your experiment is as simple as clicking Start Experiment, in the upper-right corner of your screen.
Notice the Inactive toggle switch just above the Start Experiment button? When you click Start Experiment, that switch will toggle to Active automatically. However, you can use this toggle to activate your experiment without starting it. This way, you can test the flag without actually launching your experiment (switching the toggle does not set an experiment start date; however, clicking Start Experiment does).
Note that all changes must be saved before clicking Start Experiment.
Once the experiment is running, the button is relabeled Complete Experiment. You can do this when you reach the experiment's end date, or when the experiment hits statistical significance. At that point, you can roll out the winning variant, roll everything back, or continue the experiment. (You can always revisit this decision after you've made it.)
Now that you’ve rolled out your experiment, the next step is to learn from it.