The first thing that you need to do is get an ISP (a company that connects you to the Internet). There are a number of companies to choose from, if you want one that just does the job then there are plenty of choices, many with cheap prices. If you want a premium service then you should go for a well known service, the problem with these kind of services is they tend to be expensive. You can either go for a dial-up service (it uses your phone line unaided and tends to be cheaper) or broadband (a more expensive service which is faster) whatever service you choose, make sure they have good support numbers, you may need to ring them when you get set up!
When you are connected you should have a web-browser icon on your desktop, (some common ones are; Internet Explorer, Mozilla Firefox, Opera, Netscape and Safari) double click on it and you will enter the web-browser, you use these to view websites which is what the Internet is all about).
Wait! I'm not connected yet!
Oh, sorry. Don't worry though, you've got plenty of options.