Hi Keelah,
You'll need to manually add the necessary HTML code to make a clickable link. That would look like this:
Thank You for your purchase. After downloading your files please click on the following link to go back to our website <a href="http://healingpowerhour.com">
http://healingpowerhour.com
</a>
Feel free to copy and paste that into your settings. You can also change it around, for example the following code would create a clickable link out of the text "Healing Power Hour" instead of the plain address:
<a href="http://healingpowerhour.com">Healing Power Hour</a>