There's really two ways to accomplish this. You could create a template (that you'd have to select for each page), or you could replace
page.php. Since the theme isn't written by you, you should be using a child theme so that you can still receive updates for your theme from the creator. It's good practice to keep your code separate from code that is a part of a theme, so whether you make your own template, or create a new
page.php, you should be using a child theme.
If you don't know PHP, it might sound daunting, but it's not too bad if you are familiar with HTML/CSS.
Any files that exist in the child theme will be used in place of the file from the parent theme. So you will have to make a new directory under
wp-content/themes with a
functions.php as described here.
Once you have your child theme setup, you can just create a new
page.php that has the structure/HTML from your two-column layout template, but uses the WordPress functions to show the content itself. (Also, make sure you copy the
get_footer(); bits to your new file - they do exactly what they sound like they do.)
So your main/left section would contain this (or something like it):
// Start the loop.
while ( have_posts() ) : the_post();
// Include the page content template.
get_template_part( 'content', 'page' );
// If comments are open or we have at least one comment, load up the comment template.
if ( comments_open() || get_comments_number() ) :
// End the loop.
Your right/sidebar section would contain this (or something like it):
<?php if ( is_active_sidebar( 'sidebar-1' ) ) : ?>
<div id="widget-area" class="widget-area" role="complementary">
<?php dynamic_sidebar( 'sidebar-1' ); ?>
</div><!-- .widget-area -->
<?php endif; ?>
(This is how it gets the information that you put in the
Appearance > Widgets page.)
With all that being said, if you are comfortable with HTML and CSS, this shouldn't be too hard to accomplish. I'm not sure what your experience is, so I don't want to assume anything. There really isn't an "easier" way to do this, because you are creating a brand new template. Your theme's "Blog" template will always retrieve blog posts, because that's how they set it up. If you aren't comfortable working in PHP files, you could suggest to the theme author that they add a two-column template you could use.
Best of luck!