What you should actually do is put the email inside the "Customer Responds to Survey" task. This will allow you to use the respond link in the email.
First, open the task and go to the "Event Configuration" tab and click on the "Start Process" elipses. This model runs when before anything else in this component.
When you put in a "Send Email" component in here, you'll see you have access to a special variable called "Response Page Link". Drop that somewhere in the body of the email and that should do it (though you might want some additional content, too!)
Now, you may be asking, what does that "ResponsePageLink" variable actually contain? The answer is that it will contain an html link to the survey task with whatever text you choose. By default, the text for the link will be "Take Survey", but you can change that on the "Interaction Setup" tab of the task component.
The only other thing to note is that if you have any other place (like process automation) that sends an email about the survey, then the email you insert into the workflow project itself may now be a duplicate and you don't want to spam your users.