1. In your admin menu bar, select Configuration -> Search and metadata -> URL redirects
2. To add a redirect, click the "+ Add redirect" link at the top of the page
On the resulting screen, fill in the URL you'd like to edit in the "From" field—note, http://yoursite.audubon.org/ is already filled for you. so only enter the part of the URL that comes after "xxx.audubon.org/"
Then fill in the "To" field with the existing URL that visits to the From field should redirect to. This can be the full URL of a page on your site (which includes http://yoursite.audubon.org/", just the local path (omitting http://xxx.audubon.org/ as in the directions above) or the URL to any external site on the internet.
3. If the URL you're trying to redirect already has a redirect in place, you'll be asked to edit the existing URL instead.
For instance, if many users still have links to a page on your old site that no longer works (let's say, http://ca.audubon.org/audubon-locations") you can add a new redirect to send people from "audubon-locations" to any other page on your site.