Specifying Identities for Power BI embed when generating a token

I am  the owner of the report and have no roles created. I will be embedding the report in an external application.  Everyone who has acces should be able to see everything. How do i specify the identities when i am trying to generate a token.  I keep getting the message "PowerBiEntityNotFound' when specifying the BODY in json.

I know how to get the dataset id and i assume my username is my o365 login. Where do i get the access level and role when i am the owner and my are external customers and will have all access?