How To Ad a Banner Image Link?

I would like to add a banner image link between posts on the home page, preferably in between the 2nd and 3rd posts and another between the pagination links and the footer.

I found some code that was supposed to work but couldn’t implement it because the index.php page where I needed to add the code isn’t there.

Is there another way? The one page I found some help on but couldn’t use said to do the following:

Add <?php $adcount = 1; ?> above the line containing “if (have_posts())” then add <?php if(2 > $adcount) { echo ‘your_banner_code’; } ?> <?php $adcount = $adcount + 1 ?> below the code containing “the_content” but “the_content” is not on the index.php page. Plus it doesn’t specify where the banner ad would be posted. I would like to post my ad in specific places. Is there some code or even a plugin to use?

The page I need help with: [log in to see the link]