On every purchase of ASA firewall, Cisco ships product authorization key known as PAK in printed format along with delivery. The steps remain same irrespective of ASA license feature.
1.Login to Cisco registration portal – http://www.cisco.com/go/license and enter PAK key and ASA serial number, then you will get the license key by registered email immediately.
Caution: When you enter the key in ASA you will need to reboot. Also always save the output of “show version” to keep it in your records prior to entering new key upgrade.
2.Enter the license key in ASA and upgrade software license, in this case, we upgrade sec plus.
(config)# activation-key <license>
(config)# write memory
3.After reboot, verify that new license key is accepted
(config)# show activation-key