With the plug-in installed you'll find a Print option in the app menu.
Before printing you can set a few parameters.

Canon's printer division has announced Canon Print Service, a software plug-in for your mobile device that allows you to print to compatible Canon printers via a Wi-Fi connection. The service is available for Android devices running version 4.4.2 or newer and select HP Slate devices.  

Canon Print Service uses Android's recently announced printing framework and does not require any drivers. Once installed a "Print" function appears in the options of many apps and when selected allows you to set a range of parameters including paper size, number of copies and orientation. One more tap on the Print button and your photos or documents will be sent wirelessly to the printer. 

Whether you want to send your pictures to a photo printer or print an email on the office printer, there is nothing that can stop you now. You can download the plug-in's Android 4.4 and HP Slate versions in the Google Play Store and read more about the service on the Canon website. Under the Google Play links you will also find a list of compatible Canon printers.