By default, the Cap Term Structure page opens with your default market data source setting. This is set via the Settings window > Default Settings tab > General tab > Market Data Source dropdown list.
In the Cap Term Structure page you can always see which rates you are using, even if you only have one market data source. You see this via the Market Data Source dropdown list.
In addition, if you have access to multiple market data sources rates and you have permission to toggle between those sources, you can also manually change the market data source currently used for the page for the current session using the Market Data Source dropdown list.
For more information see Changing the Market Data Source.
To change the market data source in the Cap Term Structure page:
In the Cap Term Structure page in the Market Data Source dropdown list select a different source. The page is updated using the data from the selected source.