Add customer fields

Hi,

I have searched the forum several times for more details about how to add a customer field. I did find one very thorough description about it and was about to plow through it when I noticed that it gave instructions to alter the DB table 'address_book' but it seems to me it should be the 'customers' table where the new field should be added.

Would appreciated any pointers and/or explanations about which table(s) to alter and which files (or at least how to locate the files that need to be changed).

Thanks!

Ellie