AddThis

adding google plus button

How do I add Google+ button to be visible on this site simply http://spiritsafaris.com/index.htm

I have old scipt with whcih I can do search and replace on as below
I cant find my publisher number or use of it in a script like this, on your site. Is this my number or my webdesigners ?

thank you- Richard

<script type="text/javascript">
addthis_pub = '231178';
addthis_brand = 'SpiritSafaris.com';
addthis_options = 'favorites, email,';
</script></td><td width="30"><a href="http://www.addthis.com/bookmark.php" onmouseover="return addthis_open

(this, '', '[URL]', '[TITLE]'),MM_swapImage('Share Page','','pix/btn/btn_email01.jpg',1)" onmouseout="addthis_close

(),MM_swapImgRestore()" onclick="return addthis_sendto()"><img src="pix/btn/btn_email02.jpg" alt="Share Page" name="Share

Page" width="30" height="30" border="0" id="Share Page" />