When you first log into your student email account, you may be brought directly into you inbox. If so, look in the top left corner of your browser's window and click on the Office 365 icon.
Now you are on the main page of your Office 365 account. This is where you should be able to access all of its features.
In the top right portion of the screen, click where it says "Install Office 2016".
When you click this "Install Office 2016" button, you will be asked to run or save the file. Click on "Run".
From here, follow the prompts by clicking "Yes" to start the installation, and waiting while it downloads.
You will then be able to access it from your Start button under "All Programs" or if you are using Apple from "Finder", then "Applications".