Groups require the Growth Plan. The panel will give you the option to upgrade if you don't already have this.
Currently the app will allow you to instantly upgrade your plan without taking card details, but someone will be in contact to arrange payment for the subscription.
To manage groups for your organization start by selecting the dropdown at the top left of your screen and then select Manage Organization.
Add a caption...
You can then select the Groups tab on the left. Here you can choose to Add Group.
Add a caption...
If you Add Group or edit an existing group you will see a form that allows you to set a name and description and then select the members in the group.
Add a caption...
Now when you create a reminder you will be able to assign it to a group. Only members of this group will get emails when these reminders are due.