To add a tecture to a plane, create your plane (don't worry about size right now) and open the material editor.
Select any of the materials in the editor and click the map ("m") button next to "diffuse". from the list that pops up, double click the "bitmap" texture. Now scroll down and find the "open image" (or something like that, my Max isn't open right now). This will ask you to locate and open the image you want added to the plane.
Once you've found and selected your image, check the resolution size (should be a number times combination, such as "1300x400" shown near the bottom of the file open window. Write down these numbers for later.
Now, click on the icon near the top of the material editor in the shape of a checkered cube. Select the plane, and then in the material editor, click the icon that resembles a sphere with a line coming from it pointing to a cube (or, just drag the material from the material editot to the plane).
Likely, the image will be stretched improperly. You don't have to guess and get it right. Just click the plane's modify panel and (with the number you wrote down earlier) input the last number into "width" and the first number into "length".
Don't be shocked when the plane dominates the screen. The plane just adjusted to match the resolution # you set. Just use scale and make the plane smaller until you can see it properly in the viewport. The plane should now perfectly fit the size of your image.
Hope that doe it =)
