When you run CBC/HB with interactions specified in your model, the main effect utilities plus the interaction utilities are saved to the .HBU file. When you import that .HBU file into SMRT, and when you select that utility run as the run to use when conducting market simulations, SMRT automatically takes into account the interaction effects when it computes the shares of preference for competing products. You don't have to do anything else extra.
To confirm that the simulator is taking into account the interaction effects, you can examine the utility report that by default is reported above your shares of preference results. You will see the main effects for all your attribute levels plus additional tables beneath it for any interaction effects you specified.
The total utility of a product is computed by taking the main effect utilities for the levels plus any interaction effect utilities. Those total utilities are transformed into shares of choice via either the Randomized First Choice simulation procedure, the logit equation (share of preference procedure), or the first choice voting rule (first choice).