First thing first, User Control Panel is also called UserCP, you can access it through Settings present on top left of your already login account. Look bellow highlighted area:
Now Go to Settings Page and then check right pane of My Settings and then go to General settings.
Now click on it then General Settings will open right side of it in big area, then check Messaging and Notification settings area, under it, there is one settings of Default Thread Subscription Mode, in it from list select "Through my control panel only", its all done.
FK NEW GREEN theme:
Now go to bottom of settings page and on right side near end of General settings pane, there is Save changes button, press it to save settings.
After that you can now access your future threads activity just going on you Settings page. Like this:
This is all, I think you can do these settings and enjoy subsription through UserCP. For any further guidance ask in this thread.