adding text to a text frame?

Okay, I have yet another question. I can see the text in a text frame with a script like this,

var doc = app.activeDocument;

var myTextFrames = doc.textFrames[0];

var myTF_Content = myTextFrames.contents; // this will return the string inside the text frame

alert(myTF_Content);

but how do I add some text to the beginning of that text?

lets say that this is my textFrame[0] = "this is a simple test string"

what is the proper way to add text like the number one and a period to the beginning?

Any help would be appreciated,

Duane