To obtain an OAuthClientId, OAuthClientSecret, and CallbackURL, you first need to create an app linked to your Asana account.

To create an app linked to your Asana account:

1. Log in to your Asana account.
2. Navigate to My profile Settings > Apps > Manage Developer Apps or https://app.asana.com/0/developer-console.
3. Under My apps, select New app. Specify the app name, then select Create app.
4. Once your app created, set Redirect URL to http://localhost:33333 (or a different available port of your choice), then select add.

Once you are done with creating a new app, it will be displayed on your screen. From there, you can click View Client ID to reveal your newly created app's OAuthClientId and OAuthClientSecret.