Open the photos you want to crop to the same size (File > Open).
Select the crop tool and make sure you have "No Restriction" selected for the Aspect Ratio in the Options Bar.
Click on the width field and type in the width you want. Press tab to move to the next field, and type in the Height. Press Tab again to go to the next field, and type in the resolution you want. (Use 300 ppi OR, if you're creating a digital page, use the resolution of your digital scrapbook page.)
Select your first photo and click and drag a crop outline around the area you want to keep. Click on the check mark to accept it.
Select any other photos you want cropped to the same size and do the same. No matter how large or small the crop outline, they'll all be cropped to the size you specified in the Options Bar.
