Dear viviansank,
“Full Width” is the custom Page Template, so it works only for the pages, not for posts. But if you want to hide the right sidebar on all pages and posts, you can use “Theme Options > General Settings > Display Sidebar” (select here the option “Hide”).
If you want to hide the right sidebar only on some posts, you can do it using Custom CSS. Please view the source code of the appropriate post. In the opening <body> tag, you can see unique “postid” class for each post (for example: class=”single single-post postid-1662 single-format-standard logged-in admin-bar no-customize-support”). Using this unique class, you can hide the sidebar only on some specific posts:
.postid-1662 #sidebar {display: none;}
And then you can enlarge the main content area:
.postid-1662 #main-content #content {margin-right: 0; width: 100%;}
For the next updates of LeatherDiary theme, I am considering about adding more options for displaying the right sidebar to make this theme even more customizable.
Best regards
Tomas Toman