Click 'New Evaluation License' to create a new key with an additional 30 days evaluation time.
Apply this key to your server under the Administration > License Details page.
(If you're an Atlassian Cloud evaluator, please note that we do not offer extensions of Atlassian Cloud. However, we offer full refunds during the first month of paid service following the end of the evaluation if you decide Atlassian Cloud isn't for you. After the first paid month, we are unable to offer refunds or exchanges.)