Hey mate,
I was having trouble with this too.
In the header file get the following line
<a class="publish-btn" href="<?php echo osc_item_post_url_in_category() ; ?>"><?php _e("Publish your ad for free", 'twitter'); ?></a>
and move it so that it comes directly after this
<li><a href="<?php echo osc_register_account_url() ; ?>"><?php _e('Register', 'twitter') ; ?></a></li>
Your end product should look like this
<?php if( osc_users_enabled() ) { ?>
<?php if( osc_is_web_user_logged_in() ) { ?>
<li><?php printf(__('Hi %s', 'twitter'), osc_logged_user_name() . '!'); ?></li>
<li><a href="<?php echo osc_user_dashboard_url() ; ?>"><?php _e('My account', 'twitter') ; ?></a></li>
<li><a href="<?php echo osc_user_logout_url() ; ?>"><?php _e('Logout', 'twitter') ; ?></a></li>
<?php } else { ?>
<li><a href="<?php echo osc_user_login_url() ; ?>"><?php _e('Login', 'twitter') ; ?></a></li>
<li><a href="<?php echo osc_register_account_url() ; ?>"><?php _e('Register', 'twitter') ; ?></a></li>
<a class="publish-btn" href="<?php echo osc_item_post_url_in_category() ; ?>"><?php _e("Publish your ad for free", 'twitter'); ?></a>
<?php } ?>
Hope that helps!!