Vinyl Pool brown

[Uneasy]

Hi all,

I moved to the house where landlord have 15 feet intex vinyl swimming pool. But I guess nobody was using it and it was a swamp m i know nothing about pools (yet) so I decided to make it nice again. I pumped out the water and cleaned it as much as I can. But walls are still yellow brown and I can't seem to be able to clean it. Not sure but people recommend to fill it with water and apply chemicals and that should clean it? I am not convinced and I rather clean it before I fill it with water again. Please advise what chemicals to use

[Denniswiseman]

Now that it's drained down
First try liquid chlorine (plain bleach)
Then Ascorbic acid (Vitamin C)
One of these should work then wash down and clean out before filling
You aren't on a well are you as they are a source of iron which stains badly