How can I use a computer to control the printer to print?

You can physically connect the device to the computer using the included USB cable.Check whether the corresponding icon in the device manager has the yellow exclamation mark as shown in the picture. If so, it means that the printer driver file is not installed. FlashPrint needs to be reinstalled. 

Or using Wi-Fi to make the computer and printer in the same Wi-Fi environment. For example, the device and the computer are connected to a home Wi-Fi named XXXX at the same time ,then select the IP option in the list of printer -- "about" and fill in the number in the "FlashPrint --" print "--" connect machine "option to complete the connection.(If Wi-Fi status is not connected, check whether the computer has drive by USB cable)