Power Users obtain permission to Use a Data Source in the following ways:

1. Receives automatic access to non-configurable Data Sources:  Manual/CSV Data, External Process, Existing Reports - SQL, Single Existing Report, Existing Metrics, Aggregate a Metric
2. Inherits from its Group
3. Explicitly granted on User or Data Source Editor
4. Automatically granted when user receives(explicitly or via inheritance) Edit Access to an individual element with a configurable Data Source
5. Automatically granted when user is explicitly granted Edit Access to a Dimension with a configurable Data Source
6. Automatically granted when user is explicitly granted Edit Access to a Category's elements with a configurable Data Source

A Power User can only create a new element, Dimension or Event Calendar with a Data Source for which he/she has "use" Permission.

For more information, see:

Understanding Power Users

Edit Access to Category and Elements

Edit Access to Dimensions