Article in English: This menu item is in the top-left side of the menu bar that's at the top of the screen.  If you haven't yet opened the item you wish to print, you'll first need to do so. If you can't find the File option, instead locate the ⌘ Command key on your Mac's keyboard. It's an option in the File drop-down menu. Doing so will open the Print window. If you couldn't find the File menu item, instead press ⌘ Command and P at the same time. You should see this option near the top of the window. If you're printing from online, skip this step and the next one. It's near the middle of the drop-down menu. This option will vary in appearance based on the document you're opening.  While using Safari, for example, you'll click the "Two-Sided" checkbox. If you're using Word, clicking the box next to "Two-Sided" will prompt a drop-down menu. In most cases, you'll select Long-Edge Binding from the drop-down menu. You can see the name of the currently selected printer beneath the "Printer" heading near the top of the window. To change the currently selected printer, click its name and then select the printer you want from the drop-down menu. It's at the bottom of the window. Your document will begin printing in double-sided format.

Summary in Chinese:
点击文件按钮。 点击打印。 点击份数和页数选项栏。 点击布局。 找到双面打印选项。 确保电脑连接到打印机。 点击打印按钮。