Log in to Google account, which has permission to create an Application and Service Accounts.
https://console.cloud.google.com/iam-admin
Note: To get the permissions needed to create service accounts, ask your administrator to grant you the Create Service Accounts (roles/iam.serviceAccountCreator) IAM role on the project.
On details , you can find the Application Name and ServiceAccount ID (EMAIL).
ServiceAccount ID (EMAIL) is the default ServiceAccount User; if you want to use other email IDs Folder Admin (roles/resourcemanager.folderAdmin) is required, else User will have no access to files/folders, you won't be able to index the documents.
For KEY File, click on KEYS and ADDKEY, KEY can be downloaded in JSON/P12 formats.