Go to File > Examples > Basics > Blink, and it will open the following:

If you are using one of the Arduino Nanos, please note that you need to download and install the CH340G driver because it is a different chip on board. Follow the links on this page and download the driver for your respective operating system. You will need to restart your computer after the install. Note: not yet successfully tested on Mac

The buttons at the top of your sketch, are Verify, Upload, Save and Load and there is a dropdown that allows you to pick your board and model. On Windows, this may say Arduino Uno on COM3 for instance. The first time you use it, it may say Unknown instead of the board name.

Note: TinkerCAD allows you to simulate, not only your electric circuit, but also the code running on the board.