Both the source and destination URL should be the full URL, as you would type it in your web browser.
Comments are useful to remember why you put a redirect in place - especially if it’s important and you don’t want somebody else to change it or delete it by accident - it’s often helpful to put your initials if more than one person works on the website.
The status field tells you whether the redirect is active (Published, or Enabled) or not (Unpublished, or Disabled). There are also other statuses including Archived and Trashed, however the first two are the ones which are most often used.
When the link is saved, you will see it appear in the list with a black tick in the first column, indicating that it is an active redirect.