You will need the Full Write Financial permission to perform this action.
Navigate to the batch you want to delete and select "Delete" from the "Actions" menu in the top right area.
You can also do this from the batch listing screen. Simply select "Delete" from the drop down menu at the end of the row containing the batch you want to delete.
A confirmation message will appear letting you know that all transactions within the batch will also be deleted. Click on "Yes" to finish deleting the batch.