Each workout of your competition may have different lane requirements based on the stage it occurs on, the equipment available, or your preference as the architect of the competition. You can manage all of that and more within Heat Parameters.
From your competition dashboard, navigate to "Scheduling", then "Heat Parameters."
From here, you can adjust the duration of workouts, the transition time between heats, if you want to swim lanes, and the number of lanes available based on the workout.
Please note that to adjust the heat parameters for workouts, your workouts need to be created. Check out this article for more on setting up workouts.