The Readme file from that project also contains import instructions: https://github.com/Adobe-Marketing-Cloud/aem-communities-ugc-migration/blob/master/README.md#importi...
Once you've configured ASRP as your storage type, performing the import will automatically move your UGC into the cloud storage. You'll still need to create the forums / blogs / comment sections etc that you wish to populate, but then you'll be able to populate it with your old UGC content.