Improve documentation for shipments

docs/sell/shipment.md

@@ -2,4 +2,70 @@
 title: Shipments
 ---
 
-## Shipments
+## Shipments
+
+Shipments are used to track sales items when they are shipped to customers. Multiple shipments can be created against a [Sales Order](./so.md), allowing line items to be sent to customers in multiple deliveries.
+
+On the main Sales Order detail page, the order shipments are split into two categories, *Pending Shipments* and *Completed Shipments*:
+
+### Pending Shipments
+
+The *Pending Shipments* panel displays the shipments which have not yet been sent to the customer.
+
+- Each shipment displays the items which have been allocated to it
+- Pending sales order items can be allocated to these shipments
+- New shipments can be created if the order is still open
+
+{% with id="pending-shipments", url="sell/pending_shipments.png", description="Pending shipments" %}
+{% include "img.html" %}
+{% endwith %}
+
+#### Creating a new Shipment
+
+To create a new shipment for a sales order, press the *New Shipment* button above the pending shipments table.
+
+#### Completing a Shipment
+
+To complete a shipment, press the *Complete Shipment* button associated with the particular shipment:
+
+{% with id="complete-shipment", url="sell/complete_shipment.png", description="Complete shipment" %}
+{% include "img.html" %}
+{% endwith %}
+
+Alternatively, pending shipments can be completed by selecting the *Complete Shipments* action from the sales order actions menu:
+
+{% with id="complete-shipment-action", url="sell/complete_shipment_action.png", description="Complete shipment" %}
+{% include "img.html" %}
+{% endwith %}
+
+### Completed Shipments
+
+{% with id="completed-shipments", url="sell/completed_shipments.png", description="Completed shipments" %}
+{% include "img.html" %}
+{% endwith %}
+
+### Shipment Data
+
+Each shipment provides the following data fields:
+
+#### Reference
+
+A unique number for the shipment, used to identify each shipment within a sales order. By default, this value starts at `1` for the first shipment (for each order) and automatically increments for each new shipment.
+
+#### Tracking Number
+
+An optional field used to store tracking number information for the shipment.
+
+#### Invoice Number
+
+An optional field used to store an invoice reference for the shipment.
+
+#### Link
+
+An optional URL field which can be used to provide a link to an external URL.
+
+All these fields can be edited by the user:
+
+{% with id="edit-shipment", url="sell/edit_shipment.png", description="Edit shipment" %}
+{% include "img.html" %}
+{% endwith %}