Localytics in-app messages can be generated codelessly using our creative builder, or you can upload custom HTML/CSS/Javascript which will be rendered as a web view. You may want to include a call to action (also known as a CTA) within the creative that, when clicked, links the user to a location outside of the app (like a website).
If you are uploading a custom creative, you will need to append two parameters to the end of your URL to tell the Localytics SDK to open the link outside the in-app message and to tag the impression. The parameters that should be appended are ampExternalOpen and ampAction.
Here is an example of a properly-constructed link that, if clicked within an in-app message, would send the URL-clicking user to the Localytics Docs site: http://docs.localytics.com/?ampExternalOpen=true&Action=click