Invigorator animates by using sets which contain one or more objects. The pivot point of each set is determined by the first object or objects added to an empty set. The pivot point stays at that location until the set is emptied again.
The simple solution is to add a null object, like a small cube, to an empty set. The pivot point is now the center of that cube. Next, add the letter or word to the set and move it in the set-up window to the location you want, relative to the cube. The letter or word will appear to pivot from the center of the cube, rather than from the center of the letter. You can now either turn off visibility of the cube or delete it from the set.
Does this help? If you need more, search the archives for pivot point. This is a frequently asked question.