moving Photos Library to External Hard Drive

I'm looking to move my entire Photos Library to an External Hard Drive in order to free up space.

My friend sent me the following link which had step by step instructions.

http://iphone.appleinsider.com/articles/15/01/25/how-to-safely-move-your-macs-ip hoto-library-onto-an-external-drive

I started the step which has the following instruction listed below.

To begin moving your library, open iPhoto, click File in the Menu Bar and select Switch to Library.

When I open Photos and click File, I don't even have the option to Switch to Library. What am I missing here?

I'm running Yosemite 10.10.3