Before using Cloud Composer, you must create a GCP project and enable billing.
You can use an existing project with Cloud Composer or create a new one. If you are using an existing project, you need to enable the Cloud Composer API. To create a project and enable the Cloud Composer API:
In the GCP Console, select or create a project.
Make sure that billing is enabled for your project.
To activate the Cloud Composer API in a new or existing project, go to the API Overview page for Cloud Composer.