To add a signature or image, first, you need to have image or signature and upload it somewhere like Flicker, photobucket or in your FTP. Then follow the below steps..
1. Go to your blog inside the Blogger Dashboard and click on design.
2. Then click the Edit HTML button.
3. Check the Expand Widget Template box.
4. Find by Click CTRL-F and copy and paste the line below in the search box to search for it in your code.
You will get:
4. Under that line, paste the below code and change IMAGE URL to the url address of your signature image (it’s the Direct Link of your image).
5. If you want to create hyperlink (clickable) for this image, then paste the below code and change both src & href url of yours.
You are done!