Summarize this article:

Most physical in-store items will have a barcode located somewhere on the packaging, so simply start by finding the item whose price you want to know. Produce and bulk goods tend to be the exceptions to this rule, though both of these categories typically list their prices per pound (or kilogram) anyway. Item barcode locations will vary, so look all over the packaging to see if you can find the barcode. If you can't find a barcode anywhere, it may have rubbed off or been improperly placed. Try grabbing another item, or ask a store attendant to look up the item's SKU number. Many stores have public scanners that you can use to scan an item's price. If you're working for the store or you have access to a third-party scanner, you can use the scanner provided to you instead. If you're scanning items using a flat scanner as used in most grocery stores, go to the scanner's location. Aim the scanner's red laser at the barcode, then press the scanner's button (if necessary). If you're scanning using a flat scanner, simply swipe the barcode across the flat scanner's surface. Most scanners will beep once your scan has been registered. Once the scanner beeps at you or otherwise indicates that your scan has gone through, you can move the item and/or scanner away from the scanning area.

Summary:
Find an item to scan. Look for the barcode. Grab a barcode scanner. Scan the item. Remove the item from the scanner area.