Copy-paste this html in your web page code where you would like to see the button.
That is all you need to get started. Enjoy !
To show this button below each post, open wp-content\themes\<YourThemeName>\index.php in a notepad and copy the below html between <div class="entry"> and </div> tags. Remember to save the changes.
If you want to include the button below each post, click on 'Edit HTML' and select the 'Expand Widget Templates' checkbox. Then paste the code below right after <div class='post-footer'> tag. Save the template.
If you want to include the button below each post, paste the html below into your Advanced Template, right after the 'entry-body' section. Save the template.