How to Edit Header and Footer Of Wordpress Website

I am not professional developer but I have good experience working on CSS and HTML. I want to improve my website http://sixsensebusiness.com/.

I have tried to edit it from wp-admin but It didn’t work. I have back of this. I am tried to edit files using Dream Veiwer. But I don’t know which file need to edit. I need little guidance so that I can improve it little more.

The header and footer files are in the theme folder


/path/to/your/wordpress/wp-content/themes/your-theme/header.php
/path/to/your/wordpress/wp-content/themes/your-theme/footer.php

They’re PHP files with HTML in them, so make sure you know what you’re doing and take a backup before editing them.