Use Hess's Law to find the change in heat of 2C(graphite)+H2(g)-->C2H2(g)?

Given:
C(graphite) + O2(g) --> CO2(g) change of heat rxn = -393.5 kJ
2H2 (g) + O2(g) ---> 2H2O (l) change of heat rxn = -571.6 kJ
2C2H2 (g) +5O2(g) ----> 4CO2(g) +2H2O (l) change of heat rxn = -2598.8 kJ

And please show how you found the amount in each of the equations...I'm confused whether or not I should multiply 2 on the first equation or use the amount as it is and if I should divide by 2 for the second equation because there is twice as much H2 in the second equation because there is twice as much as in the first given equation.