Denoising in Octane Render
Step 1 (Activate the Denoise Beauty Pass)
Check the Beauty Box, which you can find in the Properties panel > View Layer Properties > Passes > Denoiser.
Step 2 (Activate Octane Camera Imager)
Tick the Box Octane Camera Imager (Render Mode) Which you can find if you select a Camera in the Properties panel > Camera Properties.
Note that this setting only relates to the selected camera. If you are using multiple cameras, you have to do this and Step 3 for every camera on which you want to use the Denoiser.
Step 3 (Activate the Denoiser)
Tick the Enable Denoising and Denoise Volume Box which you can find if you select the camera in the Properties panel > Camera Properties > Octane Camera Imager (Render Mode) > Spectral AI Denoiser:.
Step 4 (Switch to Compositing Workspace)
In the Compositor you can set, what should happen with the Image after has been rendered. Here, you want to denoise the image. Blender already set up a working space for Compositing, to which you can switch by clicking on Compositing at the top of the window.
Step 5 (Activate Compositing Nodes)
To activate the Nodes in the Compositor, you need to click on Use Nodes.
Step 6 (Connect DENOISED with Image Input)
Connect the OctDenoiserBeauty Output of the Render Layers Node with the Image Input of the Composite Node.
To get back to the default Workspace, just click on Layout at the Top of the Window.