Turn off the power switch on the back of the case and remove the side panel. Most cases have thumbscrews, but older cases may require the use of a screwdriver to open. Many cases will require you to remove both panels in order to secure the hard drive, though some have removable housings. Before you begin working on the interior of your computer, make sure you discharge any electrostatic charge you may have. If your computer is still plugged into the wall (with the switch off), you can touch any of the exposed metal of the case to discharge. You can also touch a water tap to discharge your electrostatic charge. The safest way to work inside of a computer is to wear an antistatic wrist strap while working on the computer. The location will vary depending on the case, but it can typically be found beneath the optical drive bay. If you are upgrading or replacing a hard drive, you should see one already installed. Locate the HDD you wish to replace and disconnect each of the two cables coming out from the rear of the drive. If you are adding storage to your existing configuration, you should leave the original hard drive installed where it is and skip down to Step 5. Notice that the cable on the left is insulated and has a wider connector than the other. This is the Serial ATA power cable which connects the HDD to the computer's power supply. The flat, red cable on the right has a smaller connector. This is the SATA Data Connector which connects the hard drive to the motherboard. Disconnect each from the drive by pulling gently on the connectors. The method for securing the HDD into the drive bay will vary somewhat from system to system, but it typically requires two small screws on each side of the drive that hold it in the bay. Remove the screws and slide the old HDD out from the drive bay. The old drive has now been removed. If your case permits, try to maintain some space between the new drive and any existing drives to help promote airflow and cooling.  Be sure that the metal side faces up and the black,...

TL;DR in Chinese:
关闭你的电脑。 身体触地。 找到硬盘仓。 拔出老硬盘驱动的链接（如果是要移除的话）。 移除老硬盘。 插入新的硬盘驱动到空仓里。 固定驱动。 连接SATA数据线到硬盘。 连接数据线到主板上。 完成安装。