Hi Razvan, there are two ways to apply your licenses, the older way and the new way. The new way is just linking your XIQ instance with your Portal account, so all license updates are automatically communicated to XIQ for you. To do that you'd want to go back to the License Management page and click the "Link my Extreme Portal Account" button at the top of this page.
If you don't want to do that, or are unable to for whatever reason, we can try the old way of entering each key in manually. The licenses themselves are 30 characters long, including both letters and numbers, with a dash every 5 characters. For example (this is not a real license key)- AB1CD-2EF34G-H5IJ6-78KLM-N9OPQ-R12ST. Once you find your license key, you'll want to go back to the License Management page, scroll down to the Legacy Entitlements section, and click on "Enter it here" next to the text "Do you have a Legacy Entitlement Key?".
Hope that helps!