Update wordpress theme

Hello,

For my website am I using the following theme: https://themeforest.net/item/wellnesscenter-beauty-spa-wordpress-theme/12433859

and somehow I always thought that it was updated automatically, turns out it doesnt.

Now am I looking for the best/easiest way to update the theme. I’ve googled on it and found this website: https://premium.wpmudev.org/blog/upgrade-wordpress-themes-even-if-they-are-customized/

But honestly it seems to much work for such a simple and important thing. I also saw that there are plugins that can help me with updating the theme (Correct me if iam wrong.)

So, I hope that someone can tell me what is the best way to update my theme 🙂

Kind regards,
mrjobby