NOTHING is wrong – so you don’t have to correct anything.
You just need to use the classes (as I said above) to position your images.
I assume all your posts/entries are inside a div class “entry” and inside that ALL your images ae floated to the left, by default – see the
.entry img { etc....
rule in your stylesheet.
Next, if you want your image centered, you add the “centered” class to the code:
<img src="whatever.jpg" class="centered" alt="" />
For right:
<img src="whatever.jpg" class="alignright" alt="" />
Also, you can add the class “noborder” if you wish so.
If you want to maintain a site and modify themes – get familiar with CSS and other basic stuff.