this is the steps how to assign a picture to the plane..

1) Select the plane.

2) Right click (hold) and select assign new material ---> lambert.

3) a window will open on the left side ---> click ( file ) not the menu file but the one with a picture next to it showing a drawing of a mountain and a sun.

4) then press the file icon on the attribute editor on the right of ur screen ( this will open a browse window )

5) Select the picture u need and press enter.

thats it.. good luck..