Welcome to ecomodder.
That's already good mileage to start with
Regarding the EM-garage :
while logged in, go to
EcoModder Fleet list - EcoModder.com
You should see a line :
Your Garage: [ Add new vehicle | Add cycle log ]
Click "add new vehicle" , then enter the car's details and give it a name.
Then you can start a fuel log for that car.
Where do you get stuck in the process ?