All themes must include wp_footer and wp_head calls. If you don’t add these, then there’s no way for WordPress to insert the necessary html/js/css, functions like wp_enqueue_style will not work, SEO plugins will have no effect, etc etc etc
wp_head goes inside the head tags, and wp_footer should go at the end of the template, ideally just before the closing body tag.
It’s also possible that you have simply turned off the admin toolbar using the option in your user settings. Changing that may re-enable it ( assuming you have done the steps with wp_head and wp_footer )