how to load a form in php source code

hi
tanks for your useful plugin, i create a register form with your plugin and get the shortcode, add a new page in wp and put the code and its work.
the problem is that i want to add some sidebar and other thing to this page. and don’t know how? when i want to do it in php and add new page to my them folder like register-page.php i don’t know how to call the form and call it with shortcode in php codes, and when i do it from wordpress admin, add new page and put the shortcode don’t know how to call sidebar like get_sidebar(‘cat’); and add it tu register page, can u help me pls

https://wordpress.org/plugins/si-contact-form/