Graham bemethavinci if you want to change the actual structure that is in the standard twig file under {% block entry_post %}
all the html is embedded in the script I suggest you start with simple changes and keep multiple backups in case of errors (and you will have errors)
It is not easy and redesigning it in my templates gave me a headache and took ages
The actual post body is in
<div class="xt_blog_content xt_text normal">{{ data.post.content|raw }}</div>
The 'social' buttons are in <div class="xt_blog_social"> and <div class="xt_social_shares">
with different versions for 'web' or 'mobile'