Creating a new scene

To create a new scene and compose existing usd files together can be achived by first creating a new scene from the UI:

Enter scene name and save in the desired location.

To start composing other usd files together, first add a root prim. The OpenUSD schema expects a root prim (default prim to be authored) in most cases

Child prims can then be added to the scene to create other composition arcs such as references and payloads:

Set the meat data for the root prim in the layer property editor. These settings will be dependant on the pipeline if assets are to be ingested into another scene

Or

Add an existing usd file as a sub-layer:

The sublayer and it's contents can be viewed in the stage outliner: