How to Insert a Link into 'Description' of a Gallery Attachment Page?

Hi,does anybody know how to Insert a Link into ‘Description’ field of a Gallery Attachment Page? I know how to know how to make a link in a post or a normal page, but can’t figure how to do it for the gallery attachment pages. I am using the Twenty Ten Theme.

This is the page: https://mountprospectstudio.com/wordpress/?attachment_id=100

This is the text (below the image) that contains the links I need to make:

Original Portrait by Amir Magal – https://www.amirimage.com
Background Images Through Creative Commons Licensing:
Ray Anderson – https://www.rayandersonimag?es.com/
Chris Palmer – https://www.flickr.com/phot?os/ginsnob/
Geoff Gallice – https://www.flickr.com/phot?os/dejeuxx/

I would be very grateful for any help.
Thanks! Bria