Cannot print wirelessly

I cannot print wirelessly. The computer always wants to print using a USB cable. How do I change to wireless?

I had to install the printer using a USB cable because when I tried the wireless method the wizard asked me to press and hold the WPS button on the "access point" and then click the OK on the wizard.I assume the "access point" is the router and it does NOT have a WPS button only a reset button. Couldn't go any further so went the USB route.

The computer recognizes the printer. They both can connect to the router. The SSID and password has been set.

I cannot find where to change the computer to printer from USB to wireless.
The printer is Canon PIXMA MX922 Wireless Color Photo Printer with Scanner, Copier and Fax .

I have another question about this WXP computer that I'm working on. Haven't done this in a long time. I want to get into the start up options and can't remember how. "Normal start, Limited start" or something like that. I seem to remember that I used command prompt to do it.