Find your positive and negative LED legs!
Remember that our LED, shinning with light, has a long and a short leg. The long leg is positive (+, red alligator clip), and the short leg is negative (-, black alligator clip). In order for our LED to shine bright, the positive LED leg must be connected to the positive side of the coin cell battery.
What's a short circuit?
What happens if the positive LED leg is connected to the negative side of the battery? The LED won't work because we've created a short circuit. OPPS! Just flip the LED around, and HOORAY, we have light! ♦