If you want to synchronize a new folder rather than an existing folder, create a folder by doing the following:  Go to the location in which you want to create the folder (e.g., the desktop). Right-click an empty space. Select New  Click Folder  Type in a name. Press ↵ Enter. Add files to the folder by dragging and dropping them onto the folder's icon. Click the Windows logo in the bottom-left corner of the screen. The Start menu will pop up. Click the folder-shaped icon in the lower-left side of the Start menu. Go to the location of the folder that you want to synchronize, then click the folder to select it. It's in the upper-left side of the folder. Doing so prompts a toolbar to appear at the top of the window. You'll find this option in the "Sharing" section of the toolbar. Clicking it prompts a new window to open. It's near the top of the window. A drop-down menu will appear. This option is in the drop-down menu. It's to the right of the drop-down box. Doing so enables folder access for anyone on your network for your selected folder. Click Read ▼ to the right of Everyone, then click Read/Write in the resulting menu. This option is at the bottom of the window. It's at the bottom of the window. This will close the window, signifying that your folder is now being shared with other computers on your network. In order to synchronize the folder between your two computers, both computers must be on the same wireless network.  If the computer with which you want to synchronize files isn't on the same network, connect it to the same network before proceeding. You can check your computer's current network by clicking the Wi-Fi icon in the lower-right side of the screen (Windows) or the Wi-Fi icon in the upper-right corner of the screen (Mac) and looking at the top network name. This will work if your computers are both on the same wired (Ethernet) network as well. Once you've shared the folder, the other computer should be able to view the folder's contents and add files to (or remove files from) the folder:  ...

TL;DR in Chinese:
如有必要，创建要同步的文件夹。 打开“开始”菜单。 打开“文件资源管理器”。 选择文件夹。 单击共享选项卡。 单击特定用户。 单击下拉框。 单击所有人。 单击添加。 允许其他人添加或删除文件。 单击共享。 单击完成。 请确保其他计算机与你的计算机位于同一个网络中。 从其他计算机访问共享的文件夹。