You can use it either as a regular widget or a lockscreen widget. Make sure lockscreen widgets are enabled in settings, security. Then on the lock screen slide the clock over to add the widget. Do a play store search for dash clock extension and take your pick, there are many useful and fun extensions. After you install them, the little gear in the dash clock widget let's you adjust everything
Now I have another question about the slide lock screen. Is there a way to get other icons like email or camera or Chrome and slide it to unlock and open that app?