Window Trim

The windows currently in the house are slightly recessed and trimless like these:

That window has what is called an "apron" at the bottom.

What I want to do is frame out all of the windows and paint the apron white as well so it looks more like this:

Our aprons are more like the first picture and I want to use trim like the second. I don't foresee it being a huge project...but I think it will have a big impact.