Page History
...
Go to this URL https://app.box.com/developers/services/edit/ and login using the admin user account.
In this page, create a Box Content application (type any appropriate app name)
Select a custom application and click Next.
Select Standard OAuth 2.0 type of Authentication, click the option and Next.
Type an application name, click Create App button.
Click on Configure your application button.
...
Copy the client id and the client secret values for the content source configuration. Verify the scopes and check the option ‘Perform actions as Users’. This is required if you want to crawl private information from all users.
Save the application
...
Now you can copy the "Client Id", "Client Secret" and the "API Key" information.
Save the application 
Overview
Content Tools