Are you trying to apply a texture to the plane?

If so you will need to give it a new material, in that material's attributes there will be a colour slider, to the right of it is a box, click on it and select 'file' from the menu that pops up, from here you will be able to browse for your texture. (Remember to press 6 on your keyboard to see the texture in your view port).

Hope thats what you were after.

Chris