Well, I just registered to answer this question. it was so frustrating to try to find out this option...
To enable the "grouping upwards" (or grouping by the first row) you have to go to the Outline section in the Data tab and click the right-down corner of the box. In that settings box that pops up, unselect the option "Summary rows below detail"... and it's DONE!!
I hope this helps somebody else to solve this "silly" issue...