You can use a supercharger, no problem. It's free, too.
Or any other public charger or wall box at a private residence. Those all have cables attached to plug into the vehicle, so not having one is not an issue
You will need to return the car with at least a 70% charge or Avis will ding you with a charge fee

The staff should at least have told you where to find information if they didn't have anyone familiar with Teslas at the location - there's videos and all sorts of information available on the website: https://www.avis.com/en/cars/electri...model-3-rental