The way you've described is the way I was taught and the way I was trying, when the dialogue box popped up it was blank.
However, after the program crashed (apparently my file is corrupt/I don't have enough RAM) I tried again and it worked and I was able to upload a pic and see it, and adjust it.
Then I couldn't apply it to anything, until after I added reflectivity to it, so maybe that's to do with it?
Thanks for your help.