If your chosen program has a concentration (or specialization/track) you can add or remove these to your plan in Stellic.
It's important to remember that changes made in the Stellic platform will not update your official status with your institution. To officially declare a concentration, go through your normal school's channels. Those changes will populate to Stellic automatically.
In your Track Progress view, you'll be able to see which concentrations (if any) are already selected for your plan by the 'Declared' tag on the Concentration name. Any Concentrations that are not in your plan will have a tag that says "Not in Plan".