WordPress have a very handy function, wp_login_url(), that let you add a link to your login page. However, the really nice thing with this function is that it accepts a URL as a parameter to redirect the user after successful login.
Add this code to you theme template where you want the login link to be displayed.
<a href="<?php echo wp_login_url( get_permalink() ); ?>" title="Login">Login</a>