Have my own sidebar.php file in mty theme folder but default sidebar comes

I’m making a new theme for my website and I’ve a file named sidebar.php in my theme directory but while adding a sidebar to my theme using :
<?php get_sidebar(); ?>
I’m getting a default wordpress sidebar which with some UL and LI , can’t find the widget area in my theme’s appearance menu bar in my wordpress admin dashboard. It’s an urgent work because of some problems. Hoping that you people can help me. Thanks in advance 🙂