Creating second blog page with same layout

Hello, I wonder if you can help me. I am having trouble creating a second page with the same layout as my blog page.

My blog posts include some which I have given the category ‘testimonial.’ I would like to make a second page with the same layout and styling as the blog page, but which shows only the testimonial pages.

When I use the ‘What the File’ plugin I see that the template my original blog page is using is ‘index.php’.

I have successfully populated my second page using the Posts in Page plugin, using their shortcode [ic_add_posts category=’testimonial’]. 

It seems I should also be able to use their shortcode to apply the template, but when I try using [ic_add_posts template=’index.php’] then no content loads for the page.

Do you have any suggestions?

Many thanks,

Jessica