left margin to show LOGIN

I’m using the application to restrict access to a specific page, works well the restriction, however when the format (LOGIN-FORM) appears to enter the access data, does not leave enough space on the left side of the page, I would like to have more space or appears in the center of the page. How can I do this

This is the link and the page is Intranet

http://formacionpoliticavente.com/

https://wordpress.org/plugins/restrict-user-access/