CKEditor normally shows a Text format drop-down selector just below the editing window, but the GT Editor hides this selector to streamline the editing experience. However, there can be cases where you want to use other Drupal text formats for special cases (e.g. embedding a Twitter or Facebook feed).
The GT Subtheme has CSS code that hides the drop-down, which you can find at
sites/all/themes/gt_subtheme/css/gt_subtheme.css. The lines that hide the text format dropdown box are:
Changing the Default Format Without Displaying the Text Format Selector
If you have created your own text format and want your editors to use it instead of the "basic text editor" format, you should change the order of the text formats so that yours is first/on top at