Adding Robot file in any website or blog is necessary for getting traffic on site. When Search engine search content on web it directly check the robot file in that file you write what thing in your site to be allow for search or what things to be disallow for search by the Search engine.
In robot text file you write path of your sitemap on website.If You have no sitemap add to you blog then you First generate sitemap as my last post on generating sitemap and add to blogger .The robot file you can generate by the generator or you can write your self like this:
Where to Add this robot text in blogger
|Click Image to enlarge