How do I put in a fake windo
What is it for? Are you just trying to bring natural light into your space? You might consider a solar tube. https://www.solatube.com/residential/info-center
Where in the home are you wanting to decorate to make it look like a window?
Some time ago my friend had a bedroom with one window where two would have looked better. I suggested she just make another window covering like the one she had on the operable window. It looked fine and no one could tell there was no window there,
Is this what you are looking for? https://www.hometalk.com/14056800/my-long-dark-hallway-needed-some-lights?device=desktop