As suggested above, there are various ways to change your gears. You can go bigger in the back, which may require a different rear derailleur. You can go smaller in the front by getting a compact double crankset, or a triple crankset. Or all the options if you want really low gears ! The best choice is based on what you have now, and how much lower you want to go..... just a notch, or a several notches ?

Theoretically you could get smaller chainrings, but double cranksets usually come with the smallest chainring available for that model already installed.