Hello Maria,
Connect your FTP and Go to your site’s theme folder->header.php
Cut the following code inside header.php:
<nav id="site-navigation" class="main-navigation" role="navigation">
<button class="menu-toggle"><?php _e( 'Menu', 'badjohnny' ); ?></button>
<a class="assistive-text" href="#content" title="<?php esc_attr_e( 'Skip to content', 'badjohnny' ); ?>"><?php _e( 'Skip to content', 'badjohnny' ); ?></a>
<?php wp_nav_menu( array( 'theme_location' => 'primary', 'menu_class' => 'nav-menu' ) ); ?>
</nav><!-- #site-navigation -->
and Paste the whole code just above </header><!– #masthead –>
I hope it will help resolve your issue.
Note: Use FTP/FileZilla to upload/edit the files.
Watch https://www.youtube.com/watch?v=xzxGVaoG2CY
Thanks!!