The content type used to populate What We Do is Apps. If you want to find a specific post go to Content and then filter by Content type => Apps.

To create a new entry go to Content => Add content => Apps

Make the title as descriptive as you can. Otherwise trying to find it to edit or unpublish it will be very difficult.

For the body enter what you would like to see posted under your image. Text limit is 200 characters. You may have to edit it a few times to make it look nice on the homepage. Keep the Text Format set to Basic HTML. Ignore all of the settings to the right of the page.

Enter the link and the Text for it in the special area near the bottom.