To start, let’s click Opportunities in the left menu.

I've already added a test contact for this example. 

Our goal is to set a task reminder for calling this contact. But first, we'll need to create the task. Click the Task button on the contact's card.

In the pop-up, let's go to the Tasks tab.

Here we can add a task name and description. Our task will be a follow-up phone call to review a proposal sent to the contact.

And we'll use the Assign To field drop-down to assign this task to Alpha Alpha.

Next, we'll add a due date to the task in the last field. 

Lastly, click Update to add the task to the user.

Now, the task will appear on the left side of the Tasks tab.

And it'll also show up on the CRM Dashboard for the assigned user.

Ok, so our reminder task is set. 

Next, we'll need to create a new trigger for the reminder. Click Triggers on the left menu and then click New Basic Rule in the upper right.

This trigger will send a reminder to the CRM user on the due date of the task.

For our condition, we'll select Task reminder from the drop-down.

And we’ll also set a filter. Let's select Before number of days.

Since we want to remind the user on the day of the task, we set the value to zero.

Next, we'll click Add Action on the right side and choose how we'd like the reminder to be delivered. Let's select Send email.

Fill in the email address fields, add a subject, and then create the email text.

For your text, you can use custom values. Here we've added custom values for the task name, task description and due date. 

You could also add another action, such as sending an SMS or a notification if desired.