You can add a link to an external website to a Banner.
Create a banner. go to Content on the left column while logged in the the DPS 2015 Dashboard. Click on the Add Menu (looks like a page icon with a corner turned and a plus symbol on the corner) and select Add Banner. Set the column/row sizes, add an image, and add the link to the site you need users to visit when they tap on the banner.
Add the Banner to your collection and publish it.