Posts Page help

Hi

I have a page which I have made my posts page using the reading settings in the wordpress backend, when I do this my posts show up fine on the below page

https://www.calgavin.com/test/

However I want this page to not use the current theme it uses I want it to appear slightly different but only on the posts page and I also want it to have a different sidebar.

Now I have made the page which is called blog-temp.php and the sidebar again called blog.sidebar.php but how do i get this TEST page to call this page and not the current one?