Note: Only the new articles will be filtered, the past ones won't be filtered
How to filter RSS articles:
Locate Automation on the left side of the dashboard and click it.
(Check out this guide on how to create a new RSS automation)
Once you are redirected to the Automations page go ahead and pause the automation you want to add a filter.
Go ahead and click Edit configuration.
Scroll down until you see Filtering, go ahead and toggle Filter new feed by categories.
Click Update and set live