If your computer has installed AOMEI OneKey Recovery and you have backed up system with it, then you can press F11 key to enter into AOMEI recovery environment to restore system by default. What are the detailed steps? Please refer to the following explanation.
Each time when you start up computer, you will see the following message on your monitor. When the message appears, you can keep hitting F11 key to enter AOMEI recovery environment.
If you don’t see the above message when you have started up computer, you need to keep pressing F12 key to enter into a boot menu of your computer at first (some computers may require pressing F2 key, you should check the computer's motherboard specification or computer’s user manual for detail information), then choose “AOMEI OneKey Recovery” in boot menu as follows: