How do I get the smell of cat urine out of my carpet?

You can get it out TEMPORARILY. Just shampoo the carpet. Problem is, the urine has gone through the carpet and onto and through the padding and into the existing floor. So eventually the odor will return. You've got to take up the carpet and padding, sand the floors, re seal the floors with polyurethane or shellac, then put the padding and carpet down again. Sorry. Plenty of work for that little bundle of fur that we love.

Pour the Dettol liquid over the urinated spot and try this which may change the bad odour in the room to some extent

You can get a new carpet, or look into the more expensive pet cleaners. Those will most likely actually work. I had a cat that peed everywhere, and the pet cleaner that we had worked everytime! Also, after you used the pet cleaner, you can spray it will a scented spray that you always see on the commercials. They actually work! A 3rd option would to call the carpet cleaners. They can get it out for you. Tell them that you want that spot in the corner cleaned until it doesn't smell anymore. They will do everything the can with those instructions.