how to add a custom shortcode to login or signup form

Hello i am using a plugin wordpress social login plugin that gives an shortcode for custom locations so i just wanna know where i can add it as i tried to create a new page and added a shortcode there and even in settings added that page for course signup but still on course page when u click on signup still popup shows and that will be great if i can add the social login shortcode for the popup one that will be awesome u can see both things here
this is the course page
http://www.melissalovedesign.co.uk/engagenew/courses/aenean-auctor-nec-magna-sed-mattis/

this is the custom login page and social login showing here but i want this social login shortcode in the popup form how to achieve that??
http://www.melissalovedesign.co.uk/engagenew/student-signup/