There are 2 variants of Tivoli — diesel and petrol.
(Take note that refueling the vehicle wrongly will result in additional charges that will be borne by the user, so do read the instructions!)
The first is the diesel variant. This means that the car should be refueled with DIESEL ONLY. You can identify that it's diesel by the gas cap, as shown:
For the petrol variant, the car can be refueled with PETROL RON95 ONLY. You can identify that it's petrol by the gas cap, as shown:
To open the fuel hatch, you may locate a small level on the right side of the driver's seat that looks like this:
All you have to do it pull it up and the fuel hatch will open.