How can i add adsense code in all of my post

Hi as i have seen one need to add shortcode [GARD] to enable adsense ad to the post, pages or any article, i have many old posts in my blog how can i enable adsense to my older posts? Do i have to add shortcode in every post or there is any way i can enable it in all posts at once.

Thank You
Sandeep Singh

https://wordpress.org/plugins/google-adsense-for-responsive-design-gard/