How To Make Sidebar Use Widgets

I’m making my own theme from scratch because nothing else worked for me. The code I’m using to get a sidebar is <?php get_sidebar(); ?> which works in that a generic sidebar is appearing, but when I go to the widgets page it says “No Sidebar Defined” and “The theme you are currently using isn’t widget-aware”. So how do I simply make a sidebar that I can then easily drop sidebar elements into via widgets?