Go to this website:
https://www.autodesk.com/education/edu-software/overview?sorting=featured&page=1
Sign in with your student AutoDesk account you will get a screen like this:
Scroll down to the product you want and click on GET LICENSE
Fill in the required drop down menus as needed (picking non-network license if you have the option) and choosing the version you want.
After doing this, you will get a serial number and product key. Your options might not be exactly what is shown below.
When opening the CAD product, enter the serial number you received. It is also immediately emailed to the account you signed up to with AutoDesk.