How show message to login before being able to ask or answer a question?

The first step integrate DW Q&A plugin with your themes follow steps

1. Create a new “dwqa-templates” folder
   Go to your theme folder wp-content/themes/your-theme-folder folder and create a new folder named “dwqa-templates”.
2. Past DW Q&A templates to newly created folder
   Go to the /wp-content/plugins/dw-question-answer/templates and copy all file and past into /wp-content/themes/your-theme-folder/dwqa-templates

 

The second step add a login form to question page

1. Go to the /wp-content/themes/your-theme-folder/dwqa-templatesanswers.php
2. Go to line no 28 and replace <?php else: ?> with below code

<?php
else:

$args = array(
  'echo'           => true,
  'remember'       => true,
  'redirect'       => ( is_ssl() ? 'https://' : 'http://' ) . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'],
  'form_id'        => 'loginform',
  'id_username'    => 'user_login',
  'id_password'    => 'user_pass',
  'id_remember'    => 'rememberme',
  'id_submit'      => 'wp-submit',
  'label_username' => __( 'Username' ),
  'label_password' => __( 'Password' ),
  'label_remember' => __( 'Remember Me' ),
  'label_log_in'   => __( 'Log In' ),
  'value_username' => '',
  'value_remember' => false
);
wp_login_form($args);

   endif; ?>

Now user show login message when user trying to give the answer without login

If you give the register button then past below code

<?php '<a href="'.wp_registration_url().'"><input type="button" class="button button-primary" value="Register"></a>' ?>