I just got a new Apple iPhone and I would like to know how to set up iMessaging and if it is fre

[NFtoBC]

Try here for set-up info:  http://www.apple.com/ios/messages/

iMessage uses your data plan. Therefore it will be free up to the limits of your included data. Also, iMessage only works between Apple devices.

[KittyGumDropz · Accepted solution]

As a follow up on NFtoBC's answer, you can use the iMessage like a regular text(just follow the procedures indicated on the link provided) to avoid data charges(if you don't have a data plan) but you still have an option to use your icloud or apple ID for the iMessage as long as you have a data plan to cover it because the Apple ID works the same as how email does. To cut the explanation short..
using your Phone Number: No need for data
using your iCloud/Apple ID: Needs data and charges may apply if you don't have a data plan

For more explanation, I found this link in google. http://www.ilounge.com/index.php/articles/comments/using-imessage-without-icloud/