You can get a professional level recording software package for free here:
http://reaper.fm/
If you like it you can pay $50 for the licence but you don't actually have to...
This software does pretty much everything that Cubase and ProTools but it's around 20 times cheaper.

Next you need to get the sounds into your computer. To do this you need a soundcard, your pc may already have one onboard (most do). Chances are if it is a stock card you will only have an 1/8 inch line in (the size of a walkman plug). Problem is that the line out from your guitar is a 1/4 inch so you will either need an 1/8 to 1/4 inch jack plug OR ideally a new soundcard. Lots of choice out there, just make sure the card you get is for making music and not gaming.
Alternatively, if you get a unit like the PODxt you can use that as a multi effects unit and soundcard (it hooks up to your pc through a usb connection). Depends on what your budget is and how much you want to be able to do.