Help with picture sizes

Hi I am trying to create a photobook but I am having trouble with the sizing of my pictures. I know I should save them as 180-200 dpi, but I have them at 300dpi and they don't seem to fit correctly into the layout boxes. I can resize them on my photo editing program (PSE) but I don't know the dimensions of each of the holes for the pictures, is this listed somewhere so I can have an idea how I have to crop them.
TIA,
Yanelis