You have to change $new_side_bar = get_field(‘ACFSideBarField‘)
ACFSideBarField to your custom-sidebar-name-field slug.
And thats all
Every time when wordpress will try to call function get_sidebar() it will check existance of the field ACFSideBarField in curent post and if find will change the name of sidebar for loading.
Sorry for my english )) I speak russian most of time =)
P.S. that code block was for functions.php of your template. Just place it for example at the end of file
