How to connect iPad to Canon printer PIXMA 568 via wifi?

Since your printer isn't on the list of AirPrint capable printers, http://support.apple.com/kb/ht4356, your options are as follows:

1. Download the app for your printer manufacturer or a printer app that will print to several different makes of printers such as Print Magic, Printer Pro, etc. In order to print you must send documents, photos, etc. to the app.

2. Load a program on your PC/MAC that will allow your shared printers to appear as AirPrint printers. A few programs to look at are Printopia, AirPrint Activator, FingerPrint by Collobos.