Step One: Obtain a Salesforce Developer Edition Organization

If you are not already a member of the Force.com developer community, go to developer.salesforce.com/signup and follow the instructions for signing up for a Developer Edition organization. Even if you already have Enterprise Edition, Unlimited Edition, or Performance Edition, use Developer Edition for developing, staging, and testing your solutions against sample data to protect your organization’s live data. This is especially true for applications that insert, update, or delete data (as opposed to simply reading data).

If you already have a Developer Edition organization, verify that you have the “API Enabled” permission. This permission is enabled by default, but may have been changed by an administrator. For more information, see the help in the Salesforce user interface.