Choose “S3 (Amazon Simple Storage Service)” from the drop-down list.
One of the fields shown is “Server:” and it is empty, as though the user needs to type something in there.
This is confusing as many users won’t know what to enter there. In fact, the field can be left blank. Ideally it should be disabled, removed from the form, or at least pre-filled when the user is setting up an Amazon S3 bookmark.