Open your MacBook, and go to the App Store. ·         Type macOS in the search bar. ·         Select your required version from the result list. ·         Click on the Download/Get button. ·         The installer will take some time to complete the installation. ·         On completing the downloading process, tap to ‘Continue’ button. ·         The installation process will start automatically.   ·         You will have an upgraded version within a few minutes.