Step 1: From the top navigation, click on the Content drop-down and then Lists.

This will bring up the listing page that shows all List Groups.  You can browse into a group by clicking on the title, to see a list of all List items within the group.

Step 2: Search for the List item you wish to edit, or select from the list of all List items.
To search, type the partial name of the List item title into the search bar and then hit your enter key. The newly filtered list of List items will appear showing those matching your search criteria. To edit a List item, click on the Title. This will bring it into Edit mode and populate the Edit dialog with the existing field's content.

Step 3. Edit existing fields or fill out additional ones.

Step 4: Status the Content. 
Using the status bar make the content live on your website by clicking the Publish button.

Note: To view the content prior to publishing you can use the preview feature. This will show exactly how the content will look once published. To preview click the Preview button (content must be statused as draft prior to previewing).