CP with voucher code only

[soheil.amiri]

Hi dears
how can i configure CP to show only Voucher code filed ?
and i need a step by step guide to change CP login page.
thanks

[soheil.amiri]

hi
thanks from Calvin Bui for this post, i found a way to create a login page that show only voucher filed.
i change this particular code to :

<div class="form-group">
                  <input name="auth_voucher" type="text" placeholder="Voucher" class="form-control">
                </div>
                <input name="auth_pass" type="text" class="hidden" value="password">
                <input name="redirurl" type="hidden" value="captiveportal-success.html">
                <input class="btn btn-lg btn-success btn-block" name="accept" type="submit" value="I Agree">