Vinod, Mendix has a builtin login mechanism. This login form will be injected in the mendix app with javascript. So you just need to set your project security to show the login page.
Alternativly, there is a login widget which you can place on a form, in the appstore: https://appstore.mendix.com/link/app/Login%20form
Samet, top marks - that worked. It's a lot easier then I thought. - I'll look into the Widget solution later.