About Image Gallery-Unable to find the Widget in the Post Editor


I am a newbie . I wanted a image gallery for my blog, chennairealties.in, and pasted the code you have given in the post,“Create Image Gallery For Blogger With Control Options” . Now the Gallery widget is visible in all the published posts, ofcourse, without any photos… But I do not find the widget in the post editor to enable me to configure it or upload photos.I do not know how to include it inside the post editor using Layout Widget. Kindly help