What theme are you using?
If it's bender (might work for other themes too)
Open header.php and add the following
<ul id="header-links">
<li>
<a href="https://www.facebook.com/" target="_blank"><?php _e("Facebook", 'vendorpro'); ?></a>
</li>
<li>
<a href="https://twitter.com/" target="_blank"><?php _e("Twitter", 'vendorpro'); ?></a>
</li>
<li>
<a href="https://www.instagram.com/" target="_blank"><?php _e("Instagram", 'vendorpro'); ?></a>
</li>
<li>
<a href="https://plus.google.com/" target="_blank"><?php _e("Google Plus", 'vendorpro'); ?></a>
</li>
</ul>
and in footer.php if you want them to show up as links you can add something like this
<ul id="footer-links">
<li>
<a href="https://www.facebook.com/" target="_blank"><?php _e("Facebook", 'vendorpro'); ?></a>
</li>
<li>
<a href="https://twitter.com/" target="_blank"><?php _e("Twitter", 'vendorpro'); ?></a>
</li>
<li>
<a href="https://www.instagram.com/" target="_blank"><?php _e("Instagram", 'vendorpro'); ?></a>
</li>
<li>
<a href="https://plus.google.com/" target="_blank"><?php _e("Google Plus", 'vendorpro'); ?></a>
</li>
</ul>
dont forget to replace vendorpro with your theme name for example bender
once done you can use css to make the header links on one line while keeping the footer ones as a list
Good luck.