You are in luck because the tour is going on right now! go to ticketmaster and search for American Idols Live, and you should be able to locate them. You can purchase tickets there to see American Idol Live! tour 2010.
The easiest way to get tickets for the American Idol tour would be to contact Ticketmaster or visit the official American Idol site. If those two places don't have tickets you might want to call the venue that the concert will be in.
The tickets are available through ticketmaster. If you head to their website you can order directly, find a telephone number to order from, or a physical location.
