The Composer is a node-based tool. Here you will learn about the mechanics and functionality of nodes.
The video above explains how to use nodes, for a written explanation, read the following:
Nodes are the foundation of the Composer system and can be used to create and compose interactive, multi-node streamable VR experiences. Every node is comprised of one video file and a timeline on which exit flags and audio files can exist. Every node has to contain a video asset.
To add a node, drag a video asset from your videos folder or right-click on the Composer canvas and then edit the node and select a video asset from the drop down menu.
There are several ways to interact with a node. To edit the node name, double click on the node name while using the arrow cursor, not the hand cursor, located at the top left of the composer, then type in a new name for the node. You can edit the node by right-clicking anywhere on the thumbnail image. When you're on the detail page for the node, you can change the volume of the selected video file, along with select a new video file to fill the node based on your uploaded assets.
You'll have a variety of options for editing your node at the top left of the composer while selected on a node, such as duplicating, or deleting.