How to Send an Email when added a News Post in SharePoint Online site

Hi John Edward Paredes there are a number of ways that you could tackle this. You could create a Flow which has a trigger on the Site Pages library to send an email to a user/set of users to inform them that some activity has taken place.

Alternatively, you could use the out-of-the-box Alerts mechanism as displayed in the attached screenshot. This way you can specify whether the alerts are sent out immediately, daily summary or weekly summary.