1. Open original Image in Photoshop
2. Open the other image in Photoshop (should now have 2 tabs in Photoshop
3. Click on the tab that contains the image you want to place on top then hit Ctrl+A > Ctrl+C
4. Click on the tab with the image you want underneath.
5. Hit Ctrl+V
This should now place the other image over the base image but on another layer
6. Click on the base image (In the example above that would be the 'Face' layer)
7. Go up-to> filter>liquefy - Make any adjustments you want and then click OK
When in Liquefy, follow the instructions in the video you have posted above to show and hide the golden ratio image.
I tried your steps but couldn't figure it out.
I have a few questions.
Which one is the one that's gonna be liquified? The top or bottom one?
And I tried to paste the original on top of the mask and the original was too big. And versa versa.
And when I tried to liquify I couldn't see the mask.