Setting the Window size

[Posterboy]

You just set the CREATESTRUCT to the disered width, hieght, and starting position :
Look up CREATESTRUCT in the msdn libraray
example:
BOOL CMainFrame::PreCreateWindow(CREATESTRUCT& cs)
{
if( !CMDIFrameWnd::PreCreateWindow(cs) )
return FALSE;
// TODO: Modify the Window class or styles here by modifying
// the CREATESTRUCT cs
cs.cx = ?;
cs.cy = ?;
cs.x = ?;
cs.y = ?;

return TRUE;
}