Having said that, the following photo of my grandmother and my aunt is a good example of what not to choose if you´re a complete beginner.
Well, not quite my final result. I still had to change it to sepia. For absolute beginners I intend to write a little tutorial sometime on how to do this. It really isn´t difficult though. Basically, if you´ve saved your photo as a jpg. you´ll have to change your background to a layer so that you can add a colour overlay.
And all it needed now was a border. (I´ve already written an easy tutorial on how to do that but then, all my tutorials are easy. I don´t pretend to be an expert.) I thought that a stark white border wouldn´t be appropriate so I sampled a beige tone from the photo itself for the border.