How do you use an HDMI to VGA cable from MacBook Pro to Asus monitor with only VGA port?
See if you have only VGA port on the ASUS Monitor then you need to plugin the VGA part of HDMI to VGA in Asus Monitor and then plug the other part that is HDMI in your Macbook pro.There might be a problem with you that both Asus monitor and the HDMI to VGA cable have same VGA Plugs,Like both of them are female VGA or both of them are Male VGA hence they cannot be connected together.For that problem you need to have one more cable of the opposite character to that of your HDMI to VGA and your monitor's VGA port to establish a connection between the Monitor and Macbook pro using the cable you already have. Like if you have female VGA on your monitor and on your existing cable then you need to buy male to male VGA and vice versa you have to buy female to female VGA for male ports on monitor and cable you already have. If you feel that there is some other problem than that then you can message me directly and i will guide you accordingly.