Google is your friend, so is our search function. There are several posts here and in other forums found on Google about how to do it. The link I am posting explains how to do it with an 8320. Not sure if it will work on a Bold or not. From what I know, however, is that you will need a Bb data plan to access some of the ATT hotspots in Starbucks, McDonalds, etc.
You will need WiFi service books from ATT however.
Also, you will need to be real careful and ensure you are really accessing via WiFi and not via ATT, or you might end up with a huge, unexpected data bill WIFI without AT&T Data Plan??? - BlackBerry Forums at CrackBerry.com