If you have existing Internet broadband service, take a look at your existing router to see if it is wireless capable. If it is, you'll need to enable and configure the wireless settings (not a hard thing to do but can be confusing for those that haven't played around with it before). If your router doesn't have wireless capabilities, purchase a wireless router to replace your existing router.
If you don't have broadband service, you could check with a neighbor to see if they'll share access (although this may be a violation of their agreement with their Internet Service Provider). You'll want to have your parents sign up for ISP service and either hope the provider uses a modem/router combo with wireless or you'll need to purchase your own wireless router.
Another option is to check with your cell phone provider for any wireless data plans they offer, but this only makes sense if you are truly going to be mobile with the device.
Do you already have any internet access at home (ADSL / cable / dial-up modem?) and which country are you in... the answers you get might be different.
In the UK, it would be possible on a BT line to use most any ISP (but go for one offering at least 5 GB, 20 is better, and 40 if you expect to swap video or think you will be addicted to YouTube and similar stuff (sorry, I don't bother looking at it, so cannot guess what data levels you may need - just don't get into swapping films as that would eat up your monthly quota!)
See ThinkBroadband (Link below)
In the past I've used Eclipse and Plus.Net but there are some deals at Tiscali (19.99/month including voice calls to 01/ 02/ 03 numbers, broadband and the phone line rental too - and they give you a wireless ADSL router as part of the deal but it is a contract for 12 or 18 months)
(I am not using Tiscali myself as I moved home and currently using the Three mobile network as there's no BT line here at present.)