The downloaded file will be located in Application folder. Click "Get" button to download the installer image on your Mac.
Search macOS name in app store (Mojave, High Serria, EI Capitai). However, this could be a lot of challenges if you had no clue about commands and I suggest taking a look at the other solutions in this post to avoid messing up the computer with the wrong commands. This means a lot of daily and advanced tasks on Mac can be done via text commands such as creating bootable USB installer for Mac. MacOS (formly named Mac OS X) is just a variant of popular Unix based operating system.
Method 1: How to Create Bootable USB Installer for Mac via Commands
Learning how to create a bootable macOS installation disk can be helpful in a variety of situations.