Upgrade from 1.3.5 to 1.4.1

What are the recommend steps for upgrading 1.3.5 to 1.4.1 and maintaining existing data?

Thanks

Upgrading is as simple as installing:
https://awodev.com/documentation/frequently-asked-questions#install-upgrade

It does not hurt to backup your database before upgrade. That way if something goes wrong, it can always be recovered.