Hi Sandi, Thanks for contacting us. Generally the way to achieve this is to go to the Basic Edits tab > Crop effect, select 4×6″ from the dropdown and then crop your photo. This will then perfectly match the printing size.
If doing this is causing too much cropping, alternatively you can create a Blank Canvas from the Library > Start tab, choose 4×6″ from the dropdown and select a background color that will end up printing around your photo as a border. Next drag your photo on from the Photo Basket at the bottom of the editor. Resize it so that it fits as you would like it to print. This technique effectively puts a border around your photo so that it will print without any cropping.
Please let us know if we can be of any further assistance!