Let me give you the following hints :
1 .
The slowest overall step determines the rate of the reaction. Hence, if the slowest step (also rightly called the RDS, Rate Determining Step) is of the form :
A + P ---> C + Q
then rate = k[A][P]
2.
If step 1 is the RDS :
Rate = k[H2O2]1[I-]1
3.
Those steps that are not the RDS are considered to be so fast that they are in equilibrium. Hence, you can use the equilibrium expression to express terms such as [IO-], [HOI] in terms of the reactants present in the original question. Just some algebra.