The means of renewing access to your education software depends upon your licence type.
For Institution subscriptions: The subscription will expire three years after the date of acquisition. You can check your expiration date in Autodesk Account Subscriptions & Contracts. Once the subscription expires, generate a new Institution subscription by going to the Education product page (US Site) and selecting the product you need. If you have not already re-verified your educational eligibility, you will be prompted to submit information to obtain educational access.