Unless you're a trained and licensed professional, you should never attempt to install a water heater. If you don't have any electrical or plumbing training, you could be risking your own life and safety or the safety of others on the property. You could also cause serious damage to your property or home.
To successfully install a new water heater, you need to be able to transport it, understand which additional parts you require, and obtain or possess a municipal installation permit. Your municipality will also need to inspect the finished installation, ensuring that it was completed safely.