I would go about it like this...
You appear to be using postbit_legacy so go edit the existing
postbit_legacy template.
Highlight THE ENTIRE TEMPLATE with your mouse cursor and "COPY" it to the clipboard.
Then add the following-
Code:
<vb:if condition="$post['postcount'] == 1">
<!--- SPECIAL FIRST POST TEMPLAE -->
[ORIGINAL TEMPLATE CODE HERE]
<vb:else />
<!-- Standard postbit-legacy template -->
["Paste" code you copied here]
</vb:if>
So basically your final template will be twice as big as it was. The first half is the special template only for the first post. The second half will be for all other posts.
Now just use HTML to customize the top half into the special first post you want.
Again make sure you are doing this to
postbit_legacy since that is the template you currently use.