This is a step by step guide for changing the setting of the blog post page.
You can see the example of the blog post page here
1.Open the blog post page in site setting mode
2.Choose the unique setting from the page setting on the top of the page.
Because the changes will apply to all blog post pages so there is no need for additional steps for other posts.
3 - Choose content >> the main Layout from the left sidebar
4 - Change container width and top padding.
For adding sidebar
5 - Choose sidebar >> post sidebar from the left panel of the site setting
6 - So you can change the style of the sidebar form the left sidebar
Follow the same address as we’ve mentioned in step 5 to change the sidebar layout and appearance.
7 - You can set the widgets of the sidebar from WordPress dashboard >> appearance >> widgets
8 - Drag widget that you want from the “Available widgets” to the “post sidebar”
9 - Also you can change the header and footer style from the left sidebar options.