the configuration depends on the distribution: Email Id as UserId not working in 7.11 Camunda
Have a look at the installation guide, each platform contains a chapter about configuration: https://docs.camunda.org/manual/7.14/installation/full/.
For Spring-Boot it’s in the User Guide: https://docs.camunda.org/manual/7.14/user-guide/spring-boot-integration/configuration/.
Hope this helps, Ingo