The step in question is going over how to create your image planes in Maya to use as reference while modeling (something I'd definitely recommend doing as much as possible). To ensure your planes are the same size as your image (to avoid unwanted warping of your drawing) open your image in Photoshop (or another image program available - I'll use Photoshop for example). In PS, go to Image > Image size for your drawings. It'll tell you what the hieght and width is of your image (for example: 203 pixels wide, 234 pixel high).

Using the example, go to Create > Polygon Primitives > options. In the options, you want to put your hieght and width in their respective places. However, if you create a poly plane with a size of 203 units X 234 units, it'll be HUGE. So, you're going to want to shrink it down, but maintain the size resolution. To do that, use a decimal point. So, your plane would be 20.3 X 23.4 units. If that's still too big, go to 2.03 X 2.34. The plane will get smaller, yet remain the same size resolution. Also, in the option box, take your Subdivisions Along Width and Hieght down to 1. You don't need a lot of polys for an image plane.

Now that you've got your image plane ready for your image, Right Click on it. In the pop-up menu that appears, go down to the bottom and choose Materials > Assign New Materials > Lambert. This is a quick and easy way to create a new material and assign it to an object in one easy step. The Attribute Editor of your material should appear. Click on the checker board button next to "Color." Click on the Folder icon that appears next to the input box labeled Image Name. Browse to your image and click OK. Your image should now be on the plane and at the correct size.

Hope that wasn't too complicated.