At the moment the fire looks like it is sitting on top of the smoke. We want the smoke to grow out of the fire so we need to do a minor bit of editing. Select the fire layer and add a layer mask. Use a large black airbrush at low pressure to fade out the tops of the fires. Click back onto the smoke layer and use a light yellow brush in screen mode to add more light where the fire now hides in the smoke to simulate smoke lit from inside.