The RFScene RFFluid node can be created using any of the following procedures:
Toolbar
Clicking on the "RFSceneRFFluid" button from RealFlow | 3ds Max toolbar.
Successive clicks on the toolbar's "RFScene" button will simply select the existing scene.
Menu
Clicking on the "RFSceneRFFluid" option from RealFlow | 3ds Max menu.
...
Click on the Geometry button and selecting select the RealFlow subcategory. Then, click on the "RFSceneRFFluid" option.
Auto creation
The RFScene node will be added automatically at the moment of creation of other RealFlow nodes like a RFEmitter or a Fluid. For more information check → Automatic LinkingOther RealFlow | 3ds Max nodes like RFEmitters may automatically create and link a RFFluid node for convenience.