Setup Slack Developer Portal
- Create a Slack Developer account.
- Navigate to the Your Apps section and create a new application.
- Obtain a Client ID and Client Secret from the Slack OAuth settings. Be sure to set the redirect URL to your application handling the Nile Auth requests.
Slack dashboard example

Save Client ID and Client Secret in Nile
Save the Client ID and Client Secret to your database at 
console.thenile.dev under Slack in Tenants & Users -> Configuration\