will automatically come with a wireless adapter - all of them do these days.
You'll need to buy a wireless router - it will have its own built-in broadband modem - and follow the instructions that come with it. If you have any problems setting up the router come back to this thread and ask for help.
Once you have the router up and running you'll be able to access the internet wirelessly on your new laptop. Make sure that you check to see that the laptop's wireless adapter is switched on; most of them come like that by default, but some don't, and people have become almost suicidal trying to get connected, while all the time the adapter simply wasn't turned on. There's usually a small slide switch somewhere on the front edge of the laptop.