You don't need to contact Airbnb to do this. The procedure is that you just file a claim in the resolution center, using the "send or request money" link in the reservation. Airbnb has updated the system that will guide you through uploading photo evidence for EACH item you are claiming. Make sure you have photo evidence for EACH item. After that the guest has 48 hours (I believe it is) to respond. If the guest doesn't respond or declined your request, then you can involve Airbnb (there will be a link in the resolution claim). After that Airbnb will contact you for further actions. Usually it takes a few days for Airbnb to respond to your escalated claim.
The information can also be found on this page. https://www.airbnb.com/d/guarantee in the "How to file a reimbursement request" section.