[JS] About Text Frame

I am creating a preset for my document

with(app.documentPresets.add())
{
name = "Amit";
pageHeight = "30p0";
pageWidth = "40p0";
left = "1p0";
right = "1p0";
top = "3p4";
bottom = "3p1";
columnCount = 2;
pagesPerDocument = 4;
facingPages = false;
pageOrientation = PageOrientation.portrait;
}

I did the facing page off it means that master text frame is there. I want to apply object and paragraph style to that master text frame from other script. Can you tell me how to access the object of master text frame.

--Avi