Jeff it seems that you are stuck on an aspect raio of 3:2. This is the standard aspect ratio of your cameras. This means that you can print directly to any combination of a 3:2 ratio without cropping. So you could print a 2x3, 4x6, 6x9, 8x12, 10x15, etc. However if you want to printa ANY other size you MUST crop (recommended) or strecth the image to fit the aspect ratio you want (Not recommended). So, here is how you go about this.
In Photoshop:
1. Open the image you wish to print.
2. Select the crop tool.
3. At the top of the screen just below the toolbar for File, Edit, etc is some settings for your crop. There are presets that you can use or you can manually type in your settings. For this particular shot type in the settings you want. If your image is in portrait mode type in Width = 8, and Height = 10. IF landscape then type Width = 10, Height = 8. Leave all the other fields blank.
4. Drag the crop tool over your image to select the area you wish to retain. You will lose some of your image when cropping to a new aspect ratio.
5. Once you have the area selected that you are happy with click on the checkmark at the top or press Enter.
6. Now you have your shot in 8x10 ready for print.
In Lightroom:
1. Select the image in the Library Module.
2. Click the develop Module.
3. Click on the crop tool below the image.
4. On the drop down menu next to the crop tool select Custom.
5. Type in the settings for your image. Portrait- Width = 8, Height = 10. Landscape- Width = 10, Height = 8.
6. Drag your cursor across the image.
7. Move the image around until you are happy with the selected area for the crop.
8. Hit Enter.
9 Click on the Print Module to continue with the print.