Thanks for writing in! Just head over to X -> Validation section (if you're using Pro, then Pro -> Validation), and then you need to validate your theme to enable automatic updates. For detailed information, please follow our guide here (https://theme.co/apex/forum/t/setup-product-validation/55).
Then to update, you can simply head over to Dashboard -> Updates section and you will see the available updates there. From there you can select and update.
In case if you don't see the available updates, you need to click on the Check Again button on that page.