You would need to clean the air, re oxygenate it and remove the Co2. You may need to cool or heat the planet and increase or decrease humidity levels. You wouldn't be able to mine or farm so everything would need to be brought in or somehow produced locally.

Is a city planet possible?

Since most of the Earth's surface are covered by oceans, Earth becoming a city planet would be impossible, however it is possible to build floating cities on water, thus making the city planet Earth possible. ... So Earth becoming a city planet may not happen for at least millennia.

Can Earth be like Coruscant?

Could a planet like Coruscant exist? The surprising answer is maybe, and it would sort of be like Hong Kong spread all over the world. If we assume continued food production improvements as seen over the last 50 years, we could carry around 73 billion people on Earth in 100 years and 640 billion in 200 years.