Add a Signature to WordPress Blog Posts by Editing the Functions File in your Theme
The functions.php file is located within your WordPress theme’s directory: /wp-content/themes/yourtheme/
First download the functions.php file. You can do this through an FTP program — or through a File Editor feature of your web hosting account.
Open the file in a text editor (like Notepad) and insert the code found in this blog post found on wpmudev. Replace the text for the image with the correct URL for where you signature image is located (see highlighted code here):
Or you can use text instead of (or in addition to) an image:
Save and upload the updated file back to your site.
If you need adjust the appearance of your signature you can add a CSS style to your theme’s stylesheet: /wp-content/themes/yourtheme/style.css. For example, to change the color or your text:
div.signature { color: #000000; }
And to add extra spacing around your signature image:
div.signature img { padding: 5px; } 
