Please edit page on which you want to change sidebar after title and content section you found layout and header sections.
1- Layout Settings:
in this section you found two dropdowns one of which with name (page layout) you can move layout to left and right from here.
Next dropdown with name (sidebar) from here you can choose different sidebars.
2- Header Settings:
In this section you found a dropdown with name (header) you can choose different header styles from this dropdown.
Can you please tell me how I can set default post options like sidebar position, header type and whichsidebar to display.