Labeling axes on Grapher? How does one label the axes on the Grapher tool on the Mac? I am currently using OS X El Capitan. 

Here's an image of what it looks like right now, with none of the menus s

And here's the menu with the Object menu selected, as some have suggested:
With Grapher open select the Object menu. The bottom selection is "Insert Text". This lets you type a string and move it to wherever you want. Use the arrow cursor to move the text field to where you want it.

An image showing Grapher window with "Insert Text" selected.