https://www.amazon.com/Pack--Acoustic-Panels-Studio-Wedges/dp/B010GPFRUQ/ref=sr_1_3?s=musical-instruments&ie=UTF8&qid=1474411204&sr=1-3&keywords=sound+foam

There's plenty of tutorials online about proper placement but it's really a lot of trial and error if you're room has an unconventional layout like mine

edit: also bass traps man, bass traps