Content > Gallery images
Hover your mouse over the post you want and click on Delete to remove it
Confirm deletion again with Delete
Move your mouse over the post preview and click on View
Click on … and select Delete
Confirm deletion by clicking Delete
ATTENTION: The post will be deleted from your Gallery images section and can’t be shared by your partners anymore. But on social media channels where the post was already shared, it won’t be deleted and will still show up. You’ll have to remove it from every platform manually.