How to change 'Blog' Page

Hi guys

I’m quite new to creating and amending themes in WordPress (this project is my first own created child theme!) and I am struggling with one section that I can’t get to change.

I have set the address my blog posts go to as /blog/ however when I go to that page none of the layout changes I make to it are visible when I view the site. Where am I going wrong please? Do I maybe need to set up a specific page template with the amends I want and if so how do I tell WordPress that’s the template it should use for blog posts?

Ideally what I want to do is turn off the sidebar (as I have on the other pages of the site by selecting a different template) and use J Shortcodes to create Tabs that separate the blog posts by category. I have the code set up as below but nothing makes a difference when I view the page here http://jamieflynnbase.com/blog/

<span style="font-family: trebuchet ms,geneva; font-size: small;">[jtabs
size="*normal"
theme="smoothness"
width="500" -- custom width, in pixels
]
2012 ::
[=jtab]
Italy :: wp_query::cat=2012italy&post_limits=10;
[=jtab/]
[=jtab]
Dubai :: wp_query::cat=2012dubai&post_limits=10;
[=jtab/]
[jtab/]</span>

Any help would be greatly appreciated

Many thanks