how do I add a background to my page, i'm making a lanyard for my team and need inputs as to the basics

if your page is set at 40cm x 1.5cm just double click the rectangle tool and you'll have a rectangle to page. Color the rectangle or PowerClip any image you want into it. Send to back(shift+page down). Remember to remove the outline then export all as a tif. If you just need the rectangle to be white then fill with white and remove the outline then export all.