Hi Gdub,
It seems like you are using an outdated version of the theme, so we request you to update the theme to the latest version
You can view this link for updating process: https://www.styledthemes.com/wordpress-tutorials/410-installing-updating-themes
Note: Please take a backup of your site before proceeding. Normally we use duplicator plugin to make a backup. https://wordpress.org/plugins/duplicator/.
After the theme update please follow the following steps to have the sticky menu in your site.
Go to Dashboard => Appearance => Customize => Sticky menu => And select sticky Menu => Then save it.
We hope this will be helpful to you if not then please let us know.
Thanks