Upon execution, a Facebook Lookalike Audience is created based on the offer’s settings. Execution will fail if there are fewer than 100 seed audiences in a country from the selected Custom Audience.
The created Lookalike Audience objects can be found at the following locations:
https://www.facebook.com/adsmanager/audiences?act=[Account ID]
https://developers.facebook.com > More > Tools > Ads Manager > All Tools > Audience