login option is missing on the single question page, how do I add it?

Hi mate, so sorry for my late reply, well i think that you’re using the free version of DW Q&A.
In the pro version, we’ve already have that.
In free version, you can open file : dw-question-answer/templates/answers.php
replace line 25->27 with these code :

<?php if ( dwqa_current_user_can( 'post_answer' ) && !dwqa_is_closed( get_the_ID() ) ) : ?>
 <?php dwqa_load_template( 'answer', 'submit-form' ) ?>
 <?php elseif ( ! is_user_logged_in() ) : ?>
 <div class="dwqa-answers-login">
 <div class="dwqa-answers-login-title">
 <p><?php printf( __( 'Please login or %1$sRegister%2$s to submit your answer', 'dwqa' ), '<a href="'.wp_registration_url().'">', '</a>' ) ?></p>
 </div>
 <div class="dwqa-answers-login-content">
 <?php wp_login_form(); ?>
 <?php do_action( 'wordpress_social_login' ); ?>
 </div>
 </div>
 <?php endif; ?>