You will need to give you object a new material other than the default Lambert,so create a new material (either Lambert or blinn)then middle mouse drag that material on you object.select the material in the hypershade and double click it to open up the Attribute Editor, 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 image.
To view your image on your object remember to press 6 on your keyboard to see the texture in your view port.
if the object is not just a plane and you have done some modeling on it then you have the UV map the object first.
2 x Modeling Challenge Winner