Welcome to the forum, and the wonderful hobby of Lionel trains!

Nobody is going to beat you for buying a starter set, that is what they are for! An easy, one shot start into the hobby.

The set you purchased is known as a LionChief set. It is a remote controlled set, and all LionChief sets come with the wallpack for power. A standard transformer is not used on these sets, as adjustable voltage capability is not needed to adjust the speed, like in conventional, non-remote locomotives.

The wallpack will not power any external accessories, as it does not have any terminals to hook anything to, and anyway, the power output is insufficient to power much more than the set and maybe a few turnouts (switches). You can add a few more cars if you wish. You should be able to power the train around a 4x8 foot layout without much problem, possibly a little larger.

If you purchase a CW-80 transformer, you can buy an adapter plug at a local electronics supply house and solder it to standard hook up wire, and use the current terminal track, or you can purchase a regular terminal track.

Transformers are not rated as to how big a layout they can power, but how much current they can deliver.

Here are some examples of various size FasTrack layouts.
http://www.rrtrack.com/html/lionel_fastrack_layouts.html
Running just a train and a minimum of accessories, most of the small and medium size layouts could be run with a CW-80 transformer. More accessories or a larger layout would require a more powerful transformer, such as the ZW, or a separate transformer just for powering the accessories.

Enjoy your trains!

Larry