If you feel your Cityrider rear drum brake is too loose or too tight, you can adjust it at the adjustment screw (circled in red). Screw this one in to create more tension or out in case the brake is too tight and rubbing.
Have a look at this video for more detailed instructions:
https://drive.google.com/file/d/1qJi4poO42LrapTvPHauNqj_RVdzlZjG5/view?usp=sharing