Can't find help – Getting Things Done - GTD Plan Review

I'm a newby to this app. I think it MAY be pretty good...or would be if I can reset it. But I inadvertently clicked a box that erroneously apparently completed all my goals, and I can't find a way to undo it. Neither does it let me add any more. The app looked promising and I was having fun until this happened. So I don't really know whether it's good or not. One thing I know though, there should be some way to change or undo a mistaken "completed" entry.
Review by Rootstracker on Getting Things Done - GTD Plan.