You set them up on the "Feed Owner Page" for your feed. To get to that page, go to the county your feed is displayed on and then click on the icon on the far-right in the Links column, it looks like a little man wearing blue.
On the Feed Owner Page for your feed, enter the e-mail address for your phone in the "Alternate Notify Email" field, put a check in the "Mobile Device" checkbox, put a check in the checkbox to specify that notifications should also be sent to your alternate address, and then click on the "Change Your Feed" button that is below the big textbox field.