Before adding signature,i also gave trick to make each first alphabet of your blog post show big like as we see in newspaper.You should read it too for sure how make newspaper style first alphabet..
How to add it in blogger.
1) Create a signature using MyLiveSignature or any other website.
2) Copy the Image URL.
3) Log in to your blogger account.
4) Go to Layout > Edit Html > Expand Widget Templates
5) Now search for the following code
6) Paste the following code just below the <p><data:post.body/></p>
<p><div align="left"><img src="http://your url of the signature picture you created in step 1"/></div></p>
Please provide url in above code,align =left is for to tell postion of signature below each post make it to center or right where ever you want it to place below each post.
I have made it to right as you can see below.
If you are using read more hack you may find that red line you searched twice in your html,so please add the codes after the seconline you get in codes.
Happy signing your posts from now.