work with the cinema 4D Project Asset Inspector. you can find it under Window < Asset Inspector.
The Octane Texture Manager is used bulk swap or relocate the image textures that are in your Octane Materials in your scene.
Replace is the slot to type or paste in the location that is currently being used by Octane.
With.... is the slot to type or paste in the new location you want octane to reference for your moved or new image textures.