In Blender, iNodes is an add-on. Each Blender version has its own extensions, so you get one card per version, to connect separately.
Enable the add-on
After installation, enable the add-on in Blender: open Edit › Preferences › Extensions (or Add-ons), then tick iNodes. Until it's enabled, the nodes don't show up in the compositor.
Find the nodes
Open the Compositing workspace. In the compositor, press Shift + A, then open the iNodes menu. The nodes are sorted by category, then by model family.
The fastest way: in the same menu, choose Search… and type a few letters of the model, “rodin” for example.
Your scene as input
Wire your Render Layers straight into an input of the iNodes node. There's nothing to export: iNodes captures whatever reaches this input and sends it to the model. It also works with a compositor setup, a Mix for example, or with a clip.
- On an image input: iNodes captures a single frame.
- On a video input: iNodes renders each frame of the scene's Start and End range, then sends them as a video. So set this range before you start.
Once the capture is done, your scene goes back to its current frame and its color settings. If the scene renders with Cycles, iNodes warns you first: everything will be rendered, which can take a while.
Everything else
The buttons are the same everywhere: see Anatomy of a node.