To delete a file/document in the documents library, you will need to navigate to the property you need to delete document(s) from.
You will need to go into the ‘Documents’ tab under the property name and navigate to the document folder on the right-hand side. You will then see a list of documents which you can then select the red cross to delete (screenshot below). The document will only delete once you have confirmed that you are happy for it to be deleted.
Please note that once you have deleted this document you are unable to retrieve this.