You can use the Password grant when there is a trust relationship between the user and the application.

Authenticate to ServiceNow from a Desktop or Web Application

When authenticating thrugh PASSWORD grant type you need to set the following connectiono properties:

• AuthScheme: Set this to OAuthPassword.
• InitiateOAuth: Set this to GETANDREFRESH. You can use InitiateOAuth to avoid repeating the OAuth exchange and manually setting the OAuthAccessToken connection property.
• OAuthClientId: Set this to your clientId.
• OAuthClientSecret: Set this to your clientSecret.
• Username: Set this to the username.
• Password: Set this to the user's password.
• Url: Set the base URL of your ServiceNow instance site.

1. Extracts the access token from the CallbackURL.
2. Obtains a new access token when the old one expires.
3. Saves OAuth values along with geolocation in OAuthSettingsLocation, which is persistant across connections.