So you want to change your blog template, simple enough, first you will want to ensure you have your new blog and single post pages built out and ready to go live. There are a few settings we need to change in order to get the new template pages live.
In this example, the old blog page titled blog and highlighted in blue in the left sidebar is what we want to swap out with the blog-1 page, which is our new blog template page. To do so we first want to select our old blog page in the site tab, the page and not a canvas on the page must be selected. In the right sidebar you will see the template info tab, it should be set to "post list" click the drop down menu and select the blank space at the top of the menu above "post list" to set it to nothing.
Next you can delete your old blog page or to ensure everything is working properly we can first simply rename the page to something like "old blog" and keep it just in case we want to revert back to it for any reason. To rename the old blog page simply double click the page in the left sidebar under the site tab and rename as shown below.
Finally, after we have the old blog page renamed we have two steps left. First we must now name the new blog page just "blog" so that it connects properly with Wordpress to pull your blog content. Then the only step left is to set the correct template info setting for the new blog page. Again we do this by clicking the new blog page itself, then choosing template info in the right sidebar. Set the page to "post list" for the main blog page, or to "single post" for the single post page.
That's it, you have your new blog template pages connected and ready to go, all that is left to do is publish!