Uploading "cover" photo for Facebook

Uploading a selected photo from iPhoto to my collection of photos on my FB wall is no problem as FB makes this exceedingly easy!

However, when it comes to selecting a "cover" photo for FB, I can (1) either choose one already located in my collection of FB or (2) specify where the desired pic is located on my iMac.

That's where the problem begins: After I've selected the desired pic from collections in iPhoto, how can I specify its location to FB?