I tried the Canon app without any luck at all, but the PrinterShare app is working fine.
I just used the print plugin.
You don't open the app. You print from where the document is that you want to print. If its a web page, select print from browser settings. If its a PDF or other document, select print in the document reader app. It should open a standard print window where you choose the print destination (similar to PC).
But there are so many printers, just sticking with what worked is probably best.