All of my post dividers are made to fit the Blogger Minima template and the Webtalks 3 column Minima template (more information here).
1. Log into Blogger and go to Design ---> Edit HTML
2. Download your template & save it on your desktop or somewhere else that's easy to find. (just in case you make a mistake and need to start again)
3. Find (CTRL+F) ".post"
It should look something like this:
margin:.5em 0 1.5em;
border-bottom:1px dotted $bordercolor;
4. Replace it with the code given on the page of your chosen image
(choose 2 column or 3 column size)
5. Save template and take a look at the results!
If you have any problems adding your post divider, please e-mail me for help!