Welcome to cubase SX3,,,,no harm in dropping yourself in at the deep end i suppose !!!
To be honest with you, you really should have gone for a less intimidating product to start off your recording career, as cubase is as awesome as it is difficult !!!!! But i suppose you start off with the best product with the steepest learning curve there is.
Hope that doesnt scare you off,, cubase really is the bollox in the recording world, but its also very difficult to master for beginners.
Learn the basics with one of the many " free "to download programs, and once mastered you will have a headstart with the big daddy itself.
The best place to get answers to any cubase related questions is ,,,,,
www.cubase.net,, the official steinberg forum.
You will have to register your dongle serial number in your profile or you will be locked out of the forum.
Only legit owners of cubase are allowed onto the forum to post questions, and cracked versions of the program are sussed out very quickly,, so beware if you havent got a full liscensed copy with a dongle.
If you browse thru the forum you will quickly see what a difficult ,, but advanced peice of software it is.
The most important and crucial peice of equipment you need is a decent audio interface. You can work with your computers soundcard,, but dont expect quality recordings. Most computer soundcards arent up to the job of tackling cubase, and are only a stop gap at most.
You must be running a computer that ( for best cubase performance), should have a 2.8 ghz cpu, as much memory as you can afford and a decent sized harddrive.
For best results ,, its recommended that you turn your computer into a DAW,,, solely for cubase,, with no running services in the background ( email,, internet,, etc,,,)
Steinberg do a unit called the m14 which is usually bundled with sl3, but i have seen the odd one for sale on ebay. There are many makes out there, firepod, m_audio, emu, tascam, to name just a few,,, all are speciffically designed for musicians who want to record into their computers.
So,,,,, an audio interface is the most important device in the chain and the sooner you get one , the sooner you will be able to get some quality recording done.
You could do with a decent 2 channel stereo amp and a set of monitors,, but a decent hi fi would do to start off with.
There are hundreds of different effects units and racks that some people find invaluable,,, but take your time and get to grips with the basics,,, and get a decent audio interface.
Anything you record before then ,, will be a waste of time.
Hope this helps a little,,,,
Cubase can be a scary program,,, but if you learn the basics,,, dont start to run before you can walk, and get a decent interface,, you will soon start to realise what a fantastic product it actually is,, and more so,,, what you can acheive with it in the future as your skills develop.
best of luck to you,,,,,
PS: Shave your head before getting started,,,,, you will look stupid with clumps of hair missing !!!!!!!!!