How should I incorporate oil into focaccia?
In the real "focaccia genovese" oil is mixed in the dough and added on top of the focaccia.

It is a tricky procedure, there is a video and photo sequence here; unfortunately is in Italian, but you can easily translate it with Google and video and images could help anyway.

I did many times focaccia using this recipe and it's the closest thing to real focaccia genovese I can get