There is no need to teach a bird how to fly even if they were clipped prior to fledging.
Birds have known how to fly for 100,000,000 years.
You teach them where and how to land.
Make sure they have a proper perch on the cage top then toss the bird towards the birdcage from a foot away.
Increase distance until the bird can land without flying into the cage front which can injure its chest.
Use plays stands not furniture, TV, and drapes for other landing zones throughout the house.
Cover windows and mirrors – we use dream catchers and stained glass.
Help them mentally “map” rooms – where walls are.
A panicked bird can mistake a light color wall for the sky so they have to know where walls are to avoid concussions.