How to delete RSS Feed articles:
Firstly locate Automation on the left side of the dashboard and click it.
Choose your desired Automation and click the three dots as shown in the picture, after that click View Feed.
(Check out this guide on how to create a new RSS automation)
You will be redirected to the Feed page, where you can choose the posts you want to delete, go ahead and click the three dots again, and then delete as shown in the picture.