I just grabbed an Uber from GIG to copacabana and paid 41 reais. Anyone who doesn’t use Uber from GIG is just throwing away money. To get an Uber you have to go to the departures level (2nd floor). There are signs on the floor that say “taxi” and “carro particular”(private car which is Uber) so just follow those. They lead to one of three doors. When you open up Uber it will ask which of the three doors you are at, you choose it and that’s it.