Insert blocks in an especfic type of content?

I’m trying something new with any type of content in my website
For example… actually if I enter to any node of my website, the info displayed is only:

– Header (Title)
– Navigation Bar
– Node Content
– Footer

I want to introduce sidebar right & left blocks when a user access to a node content of any type of content
There is an option on blocks that “allows” the block to show on specific type of content, for example Articles, but when I select the option my block just dissapear, it is no longer displaying in any part of my website, neither in the nodes of type Article, that is where I set it.

I don’t know if I have to modify something on my node.tpl.php of my theme to allow this feature?

Drupal version: