There is no 'treat as' option because it is not necessary. 888 include the table size in their hand histories, so PT4 knows the correct table size.
Depending on whether you are using the new or old 888 Poker software you may or may not need to configure your preferred seat using Configure > Sites & Import Options > 888 Poker. (The new 888 software auto centers you, and PT4 knows that, but in the old client you can configure your preferred seat, and you need the settings to match between 888 and PT4.)
If the stats are rotated by a consistent number of seats you can reposition them to the correct player by holding the Control key (Command on Mac) and dragging.
Be sure to PT-icon > Save Layout when you're done.
If the Hud appears while you are waiting to post the blinds (before you actually start playing) do NOT reposition the Hud at this time. It will automatically rotate your preferred seat once your first played hand has been imported, and if you move them before that it will not work correctly.