There are three options provided for single post Layout
1. Blog with Right Sidebar
2. Blog with Left Sidebar
3. Blog with Left & Right Sidebar
4. Blog with Full Width & no Sidebars
To choose single post Layout, follow the steps below
step 1 : Go to Dashboard(admin section) and Navigate to Appereance > Customizer > Basic Setting > Blog Layout
step 2 : select any one option and
step 3 : click save