You can also open header.php and find the following lines:
<ul class="header-social-icons clearfix">
<?php
// Social variables - Options Panel
$header_fb = of_get_option( 'ac_facebook_url' );
$header_tw = of_get_option( 'ac_twitter_username' );
$header_gp = of_get_option( 'ac_gplus_url' );
$header_rss = of_get_option( 'ac_custom_rss_url' );
?>
<?php if ( $header_tw != '' ) { ?><li><a href="https://twitter.com/<?php echo esc_html( $header_tw ); ?>" class="social-btn left twitter"><?php ac_icon('twitter'); ?></a></li><?php } ?>
<?php if ( $header_fb != '' ) { ?><li><a href="<?php echo esc_url( $header_fb ); ?>" class="social-btn right facebook"><?php ac_icon('facebook'); ?></a></li><?php } ?>
<?php if ( $header_gp != '' ) { ?><li><a href="<?php echo esc_url( $header_gp ); ?>" class="social-btn left google-plus"><?php ac_icon('google-plus'); ?></a></li><?php } ?>
<li><a href="<?php if( $header_rss != '' ) { echo esc_url( $header_rss ); } else { bloginfo( 'rss2_url' ); } ?>" class="social-btn right rss"><?php ac_icon('rss'); ?></a></li>
</ul><!-- END .header-social-icons -->
and change them with:
<ul class="header-social-icons clearfix">
<?php
// Social variables - Options Panel
$header_rss = of_get_option( 'ac_custom_rss_url' );
?>
<li><a href="https://yourtwitterurl" class="social-btn left twitter"><?php ac_icon('twitter'); ?></a></li>
<li><a href="https://yourfacebookurl" class="social-btn right facebook"><?php ac_icon('facebook'); ?></a></li>
<li><a href="https://yourgoogleplusurl" class="social-btn left google-plus"><?php ac_icon('google-plus'); ?></a></li>
<li><a href="<?php if( $header_rss != '' ) { echo esc_url( $header_rss ); } else { bloginfo( 'rss2_url' ); } ?>" class="social-btn right rss"><?php ac_icon('rss'); ?></a></li>
</ul><!-- END .header-social-icons -->
Also change https://yourtwitterurl, https://yourfacebookurl, https://yourgoogleplusurl with your profiles urls.