I'm not real familiar with the area, but a quick check of the map shows Rome in floyd county. So, no problem with that one, as it uses conventional FM. However, most of Cobb county appears to use a digital trunked system. Your 346 will not be able to monitor that system. While they have some conventional fm frequencies listed, I have no idea how often, if at all, they are used. If you want to monitor Cobb Co., you will have to invest in a new (digital capable) scanner.
As for programming, by far the easiest way will be using a computer to import the systems/frequencies. Freescan is a great program, works with uniden scanners and, with a subscription to radio reference, you can import directly from the database to the software.
If you want to stay with manual programming, this link,
Easier to Read BC346XT Scanner Manual, will probably help much more than I can.
Jeff.