Under the setting "Reminders and notifications", there is the setting for the weekly letter, where you can choose in the drop-down list which day the weekly letter should be sent. It is also possible to mark "Do not receive a weekly letter" if you don't want to receive weekly letters at all. Finish your changes by clicking "Save".
It is also possible to decide whether to send a weekly letter even without events or activities.
With this setting enabled, you will receive weekly newsletters even when there are no upcoming events or recent activities for that week.