Forms are normaly autocreated and a reference is stored in a global variable (Form2 in your case), if you don't indicate otherwise as pepecito mentioned.
Also remember a form is an object.
So to create a form at run-time, you have to do something like:
var
MyForm2: TForm2;
begin
MyForm2 := TForm2.Create;
MyForm2.ShowModal;
MyForm2.Free; //if you use Show, be sure to free it in an OnClose event.
end;