Here's a script that will ask to open two files. then move the top layer to the first doc and close the second file. It will then resize to 50% (you can change that) and finally move it to x=5 and y=5
var mask = '*.*'
var file1 = File.openDialog ('Open primary file', mask, false);
var doc1 = open(file1);
var file2 = File.openDialog ('Open primary file', mask, false);
var doc2 = open(file2);
activeDocument = doc2;
var curLayer = doc2.layers[0];
curLayer.duplicate (doc1.layers[0], ElementPlacement.PLACEBEFORE);
doc2.close (SaveOptions.DONOTSAVECHANGES);
activeDocument = doc1
curLayer = doc1.layers[0];
curLayer.resize(50,50);
var xPrime = 5;
var yPrime =5;
curLayer.translate(xPrime - parseInt(curLayer.bounds[0]),yPrime - parseInt(curLayer.bounds[1]));