The guys are right about the tab fields. You can either tab over to the 3rd tab, which is center justified, or you can simply go to the tab in the object inspector and set any tab you wish to center.
Take note that while this centers the text on the tab field, the positioning and animation of the text object is directly related to the pivot point of the object in question. This is absolute, so if you want to center the object, center the pivot point to the object and then set it's values based upon the resolution of the project.
#XPression