Composite Item
You can designate an item as a composite item by editing the item (Inventory -> Items) and marking Yes for the Composite Item setting.
After saving the item with Composite Item set to Yes, you can click the Add/Edit Component button to add the sub-pieces to the composite item. You can also get to this edit tool by going to Inventory -> Home -> Manage Build Orders -> Edit BOM Definitions.
You can build composite items using the Inventory -> Home -> Manage Build Orders process.
When a build order is created, Fill it to complete the build order.
You can set up the system so that composite/BOM items are created automatically during shipping by activating the BOM Auto-Create During Shipping add-on.
You can import composite/BOM definitions via a CSV file by activating the Import BOM Definitions and Build Orders add-on and going to Tools -> Import -> Import BOM Definitions.
The inventory reports section has List BOM Definitions where you can view the definitions for an item and List Build Orders where you can view pending or completed orders.