Essentially its about knowing that reactions can go both ways. To make it go more one way you can change the conditions.
If the forward reaction is exothermic (it gives off heat to the system) you can make the reaction go more this way by having low temperatures. This is because if you l=think of it as a balancing scale then if its too cold the equilibrium wants it to be equal so it shifts so its more exothermic to maintain the temperature of the system.
Let me know if you stil don't understand but I hope that helps at least somewhat