Intro to Mel Script Part 1 :: How To Find The Script Editor.

All of these screen captures come from Maya 2014 (so your version might be different than shown here).

One of the first things to learn about Mel scripting is where to find your best helper tool:

The Script Editor.Here is what the Script Editor looks like:

The Script Editor is split into top and bottom sections.

Script Editor can be found in a couple of places:

There is a menuItem in Maya's main menuBar:
Window > General Editors > Script Editor

And, there is an iconButton on the bottom right of Maya's UI.