If you would like to include a hyperlink in your metadata, you will need to format it with an anchor tag <a>.
In the example below, the anchor tag begins with: <a href= and ends with >>. In between the >> at the end is where you will insert your display text.
<a href=https://archive.org/details/ScreenlandDec1923>Internet Archive</a>
https://archive.org/details/ScreenlandDec1923 represents the webpage url you want to link out to and Internet Archive represents the text that is represented in the LUNA Viewer's data panel.
The end result should look something like this:
Click on the following link for an additional example and more information on HTML anchor tags.