Use the Menu bar on your CentOS VM console to go to Devices and select Insert Guest Additions CD Image at the bottom of the menu. This action should connect the Guest Additions CD ISO file to your virtual CD/DVD drive.
Use the Menu bar on your CentOS VM console to go to Devices and select Insert Guest Additions CD Image at the bottom of the menu. This action should connect the Guest Additions CD ISO file to your virtual CD/DVD drive.