Going from EX L capitan to mojave

When you download Mojave it will appear in your Applications folder as

Install macOS Mojave.app. You can just double-click on that and the installation

process will start.

After Mojave has installed the Install macOS Mojave.app will self delete.

So before you install Mojave make a copy of the install app and keep it safe on

an external drive. It is also possible to create a bootable USB installer using these

instructions. How to create a bootable installer for macOS – Apple Support

Keeping a copy of the installer app or making a bootable installer (16GB USB)

is handy if you ever need to reinstall Mojave and want to avoid the depressing

download process or having to use Apples Recovery Servers. Or if you want to

install on other macs you may have.

You can only get the full installer through the App Store.

Open Safari click on this link, Firefox will not work

How to upgrade to macOS Mojave - Apple Support

go to Section 4 and click on Get macOS Mojave

This will open the App Store at the Mojave download page,

it should say Get or Download.

Before upgrading make a full back up of your Mac.

Check that third party apps you use have updates available for the new OS.

https://roaringapps.com

Check that your printers/ scanners etc have updated drivers and software available for the new OS.

Connect your mac to your router via cable rather than rely on WiFi.

Do not use your mac while it is downloading

and do not use any other devices that share the same internet connection.

If the App Store says ‘Open’ then it is detecting a previous download of the install app

go to the Applications folder locate Install macOS Mojave.app.

Move it to the Trash, empty the Trash.

Restart, click on the link again, the App Store should say ‘Get' or 'Download'.

That is an update to 10.14.6 that you can use if you are on 10.14.5.

If you want to upgrade to Mojave you have to download the full installer

available from the App Store Mojave download load page. It is 6.2GBs in size.