Did you read through this document?
https://www.ibm.com/docs/en/qradar-common?topic=widgets-creating-from-generic-api-data-source
It explains about the results mapping as well. See point#6 on the above link.
Use title from the result set to On - This is optional and the explanation is given on point#7.
As far as the URL endpoint is concerned, you need to enter in the following format:
/api/config/deployment/hosts
Then try Run Query button see the output.
#QRadar#Support#SupportMigration