Here’s a quick way to add the new Google +1 button to a WordPress blog manually.
Step 1: Get Your Code
Pop over to Google’s Page about +1 and select your button style and then copy the code provided into your favourite text editor:
Step 2: Edit Your header.php File
Navigate to Appearance -> Editor within your WordPress dashboard:
Select header.php from the right hand list of files.
paste the first section of the code into the file just above the </head> element:
Step 3: Edit the single.php file
You’re already within the editor, so simply choose the single.php file from the menu. This change ensures that the +1 button appears in every post.
Paste the second section of the Google +1 code into the HTML just after the <div class=”entry”>
Step 4: Edit the Main index.php file
This is basically just a repeat of step 3. Choose index.php from the right hand menu, and find the <div class=”entry”> code in the page. This change ensures that the +1 button appears in every post that gets listed on your home page.
Paste the second Google +1 code into the HTML as in step 3.
…And that’s it.
There are probably already numerous plug ins that will carry out all of the steps above, and if you changed theme after installing your Google +1 button into WordPress using this method, you’d need to do it all again.