To be safe, it is a good idea to install all three of these drivers prior to using cms on ESP8266.
Run the following command in terminal
brew tap mengbo/ch340g-ch34g-ch34x-mac-os-x-driver https://github.com/mengbo/ch340g-ch34g-ch34x-mac-os-x-driver
and
brew cask install wch-ch34x-usb-serial-driver
Start a new terminal after the driver has finished installing.
Click here and the zip file for the driver will start downloading. Once finished, unzip and open the zip file. Click on the driver install file contained inside and the driver should start installing. Once the driver has finished installing, make sure to start a new terminal.