Automatic Data Refresh - How to do it?

You can achieve this by schedule refresh for please follow the link

https://docs.microsoft.com/en-us/power-bi/connect-data/refresh-scheduled-refresh

The main purpose of Power BI Desktop is to build reports. The Power BI Service (online) is where reporting is viewed from.

As mh2587 mentions, it's possible to set up a scheduled refresh cycle to keep the online reports up to date automatically. This scheduled refresh is like clicking refresh in the desktop app but updates the data stored online (but not your local PBIX file) and prevents you from having to republish whenever you want to update the data.

To bring the desktop file up to date, you click refresh in the PBIX or download a copy from the online service. There usually isn't much need to keep the PBIX always up to date since that file is generally used for building a report rather than viewing and sharing it.