When you drop a field object (a database field, formula, parameter field, and so forth) inside a text object, whatever formatting the field object had BEFORE you dropped it inside (either default formatting coming from the Field Explorer or whatever formatting you applied to the object on the report before you moved it) will be retained inside the text object.
To format the object if you’ve already placed it in a text object, you must edit the text object and format the individual field object within the text object.
Edit the text object by double-clicking it. Within the text object, select the individual field object. You’ll know you’ve selected it when the field object inside the text object turns black. Right-click. A pop-up menu will appear. Choose Format field object name from the pop-up menu. The Format Editor will appear. Make any desired formatting changes and click OK. End text object editing by clicking anywhere outside the text object.