Problems using the mask feature in DeNoise

I am using a Windows 10 PC with 16GB of memory. Last week I purchased DeNoise v. 3.4.2, Gigapixel and Sharpening from the Topaz Labs web page, and I just started using the programs. I am having difficulty using the Mask feature in DeNoise. I watched several YouTube tutorial videos, but I cannot duplicate what is shown on those videos. Perhaps they are for a different version of DeNoise. Here is the problem when I try to mask an area of a photo in DeNoise using the “Standard” model. I click on the Mask button under the photo in DeNoise. I then set the various parameters of the “Add” brush. Then I paint with that brush on an area of the photo which appear red to “Add” to that area. Then I don’t seem to be able to activate (apply) the change under the red overlay. Some of the tutorials show an “Apply Mask” button, but I don’t see it on my DeNoise screen. There are two other buttons: “Update Preview” and “Apply.” If I use one or the other there is no effect on the image and the box on the lower left of the photo on the left still shows “Standard Not updated.”

  1. Could you please tell me specifically the sequence of steps to use the mask feature and why I have been unsuccessful in using it. I assume I am doing something wrong.
  2. Where is the “Apply Mask” button? I cannot find it on my screen. How do I activate the Maks application?
  3. What do the “Update Preview” and “Apply” buttons do, once I paint portions of the screen red with the brush?
  4. Once I use the mask feature, how do I close it down so I can use DeNoise on the whole photo, that is, so that the red overlay no longer appears on the photo?