You can use the Fixed Schedule Card to send reminders to your users.
Add the Card
To add the Fixed Schedule Card:1
Open the Trigger menu
Right-click anywhere in your Workflow. Then, hover over the Trigger menu:

2
Add the Fixed Schedule Card
Select Fixed Schedule to add the Card:

Schedule the Card
You can use the Card’s settings to schedule when it executes:
Set a Custom Schedule
You can use a cron expression to set a custom schedule for the Card.To learn about cron expressions and test them out yourself, check out crontab guru.

