How to turn on appearance of center lines in AD and AP

[RickyO]

Being very new, I'm using a number of tutorials to assist my learning.  In many such, in both AP and AD, when they move their cursor along either the horizontal or vertical edge of the page, the center lines of the page pop-up, usually in green lines.  Mine is not doing that.

I've added a pixel layer, and doesn't matter if I'm using the pen tool, brush tools, or gradient tool, as I pass along the edges it still does indicate center lines.

Where is the setting for turning this one??

Here is the URL of a tutorial that describes it early on: 

 

[dutchshader]

turn on snapping, and try one of the shape tools.

when there is a shape on the workspace it also shows the center with the fill tool

[RickyO]

Thank You!