RegEx. Simple question

This is a newbie question. How in the heck do I turn on Regular Expression searching? I just want to run a simple search and replace for Spaces, tabs (^t) or new lines, and I just can’t seem to find this. Can someone help out a newbie here?
I’m used to using UltraEdit where this is pretty easy to find, but my company is not up for buying a copy of that. I have hunted through menus in Atom and I am just missing it.

In the find-and-replace panel, it’s the first button on the right side, which reads .*.