You need to change the setting in the print menu on your computer to print one-sided. Once you select print, a menu will pop up and you need to find the print setting that says two-sided (or something similar) and make sure that that box is not checked or selected.
Click on my screenshot below that shows my printer menu and where my two-sided printing option is located. Your printer menu will most likely look different than mine, but you will have options to change from two-sided printing.
