If you are in the SmartFit program looking at the gain adjustments screen, select the next tab “Advanced Features” and then select “Comfort” in the second row of tabs.
You will see a list of features and DFS is an item in the list. You can change the setting there.
But note that it’s a per program setting, so you need to change it in every program and you can change it one side or both sides. The default will change it both sides, which is probably not what you want. There is a black dot to show the recommended setting. You should keep it as low as you can without getting feedback. In particular the strong setting is not recommended for speech because it reduces comprehensibility.