RMA are accessible though Inventory menu. There's four menus, divided by
type. Users can access to the list of RMA or RMA lines.

Create an RMA:

1.  Select a partner. Enter RMA lines associated to an existing picking,
    or manually.
2.  Request approval and approve.
3.  Click on RMA Lines button.
4.  Click on more and select an option: "Receive products", "Create
    Delivery Order".
5.  Go back to the RMA. Set the RMA to done if not further action is
    required.