Use these suggested settings - click image below. If your photo has an aspect ratio of 7:10 you will loose part of the top and bottom, but can drag up and down for best composition. Or uncheck zoom to fill and have white borders. You will have to decide your own settings in the Print Job tab e.g. for sharpening and output adjustments. If you prefer, create virtual copies first and crop to 8:10
In the print module, click on Page Setup (Lower Left corner of the screen) and set up a print on 8x10 paper. This example is for a standard 1/8" border. Choose borderless if that is what you want.
In the Layout Panel (Right Side) at the bottom of the panel, change the width to 7.00 inches.
In the Print Job panel, change the Print to > JPEG File.
Click Print To File (Lower Right corner). Send this JPEG file to the printer.