Follow the following steps to perform an IRC calculation:

1. Take the optimized transition state structure of the reaction.
2. In the calculation setup window add the relevant data regarding the techniques, basis sets, method, step size and the direction of the IRC.
3. On successful completion of the calculation, check the output file > Results > IRC.
4. On the given plot you can choose to go in either the forward (product side) or the reverse (reactant side) direction.
5. Look carefully at the plot and the corresponding structure.