I highly recommend actually staying in the 20-60 range zones until you ding 62. The reason for this is that despite getting a slight penalty in experience for being over-level, the advantage of having flight will more than offset this. That, and WOTLK and TBC zones are the slowest part of the leveling process. Minimizing your time there as much as possible is worthwhile.
Anyway, however you choose to get to the addon's menu, choose guide list and then pick the zone you want to quest in. There are some zones that will autoselect based on quests in your log, but not all guides or all quests are set up that way. (If you don't want to switch to a guide that auto-pops up choose "not now" or "never") As you can see in the screenshot, there are various categories of guides. Most max level content (such as Argus) is found in Achievements rather than leveling.
Zygor Guides is an in-game software strategy guide for World of Warcraft. Every guide comes complete with the Guide Viewer, which displays step by step instructions of what quests to accept, how to complete objectives, when to use items, and more. Our gorgeous waypoint arrow will point you exactly where to go at all times and the model viewer will display fully rendered 3D models of NPCs and objects mentioned in the guide.