Same as this:
https://supportforums.cisco.com/discussion/10867761/cucm-7-export-license-file-upload
You'll need to generate the license file via several parameters which are provided during installation. You can generate the new license MAC here:
http://www.cisco.com/web/cuc_afg/index.html
Keep in mind that license macs are relevant up to 9.x (not including). From that point on Cisco uses ELM/PLM which requires you to create requests with ELM/PLM and send them a copy to that they can provide you with licenses according to your organization's needs.