Android 6.0 customizing lock screen clock to show seconds

[AC Question]

I am trying to figure out how to customize the lock screen clock to show seconds. (I have a Nexus 5x with Android 6.0 on the Project Fi network.) I would like to install as few apps as possible to do this. It seems that in previous versions of android you could enable widgets in the lock screen settings and then 'swipe left' on the lock screen. I see neither the swipe left, enable widgets, nor lock screen settings option on my phone. The clock widget I would like to use is the Digi Clock widget.

Thanks