The wishing well is a reward item that you can only get by scoring extremely high with the Garden Club when you try for a membership with them.
Did you download the swingset and then place it inside of your downloads folder? If so, then I'm afraid I can't help on that.
As for the fish, your pond has to be at least 4x4 squares wide and 2 squares deep. Also, you can't fish when the pond has frozen over.
EDIT: I can help with the swingset. Check out
http://www.snootysims.com it is a known issue with the bonus items. Theres a link on the frontpage there for a message from MaxoidDrea about it.