[delphi.com.ar]

No se que quieres decir con "ubicarme"...
Prueba esto:

var
  Selection: TGridRect;
begin
  with Selection do
  begin
    Selection.Top  := 5;
    Selection.Bottom := 5;
    Selection.Left := 2;
    Selection.Right := 4;
  end;
  StringGrid1.Selection := Selection;

Saludos!