Help!

Okay... I have switched back and forth from the old to the new interface and CANNOT find how to change to a 3 column layout. I've consulted the Help link and cannot find any of the tabs it suggests. Can anyone help? I would greatly appreciate any help I can get! Thanks so much.
Dianne

Under Reconstruction...

Please bear with me. I'm trying to change my blog to a 3 column layout. So far, the info I have gotten from Blogger has not been applicable. If anyone has a trick, please let me know! Thanks!
Dianne