1. Enterprise Edition
2. Unlimited Edition
3. Developer Edition
The API package is not available for the following editions:
1. Personal Edition
2. Group Edition
3. Professional Edition*
If you are an existing Salesforce customer and want to upgrade to either Enterprise or Unlimited Edition, contact your account representative.
* Certified partner applications, such as the PE version of the Excel Connector, are granted an API token once they have completed a security review. This API token is sometimes referred to as a "Client ID". API requests identified with a certified partner application's API token are allowed to operate with Professional Edition orgs.
For Enterprise, Unlimited and Developer Editions you only need to Edit your profile and select the checkbox for API.