To remove an entire submission or a single image from a collection or round follow these steps:
Navigate to the round or collection you want to make the changes. Select the round or collection from the sidebar menu
Select the submissions or images you want to remove by checking the boxes
In the "Bulk Action" dropdown at the top you now find the option to remove the submissions or images
Confirm your removal
Done.
The submissions or images will only be removed from the round or collection you are currently in. They will not be deleted from your call for entries. If you delete something by accident you can always go back to "All Submissions" to look for previously removed submissions.