How do I change the clock on my Mac to show the seconds?

Problem: I want the clock on my Mac to show seconds. Or I just want to know how to change it. How do I change the clock settings on my Mac.

Solution: coming right up, with pictures

1. At the bottom of your screen, in the "dock," click this icon

2. When it opens, click the icon that's highlighted in the picture below. It's called "Date & Time."

3. Edit this screen as desired.

4. Your changes are saved immediately (you don't need to search for a "Save Changes" button. There isn't one.