how do i install

Does your Mac hardware meet the minimum system requirements for Mojave?

https://support.apple.com/en-us/HT210190

If your computer meets the minimum system requirements, then make sure to have a good verified working backup before you attempt to upgrade the OS. There is always a possibility that something could go wrong. In fact you should always have frequent regular backups to prevent data loss.

Personally I would create a bootable Mojave USB installer to have in case the system become unbootable just in case Recovery Mode has issues connecting to Apple's servers. I would test boot the USB installer to make sure it will boot your Mac.

Once you have a good system backup you can just run the Mojave installer app located in the "Applications" folder or use the USB installer to upgrade the OS.

Open Safari to click on this link, do not use Firefox,

How to upgrade to macOS Mojave - Apple Support

Check that your MacBook Pro can upgrade to macOS Mojave in Section 1

if it does go to Section 4 and click on Get macOS Mojave.

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.