Supercharge is a really useful event that will help you progress faster. When the Supercharge event is live, you can activate it by clicking on a producer and toggling the Supercharge switch on.

The way it works is that once activated, you will see a different "Energy" icon pulsing on the Producers it can be used on. Once you tap such a Producer, you spend 2 energy instead of 1, and you have better chances at getting a higher level item than before. 

Keep in mind that you can always turn it ON/OFF from the toggle button you can see in the info panel when you click on a Producer.