How do I connect to my wireless printer (Pixma mx870)?

My family has this printer set up and they have no problems connecting to it and printing wirelessly. I downloaded the driver for this printer, connected to the printer via the USB cable, and was able to print when connected via the cable. However, when I unplug the cable, the printer status goes from online/ready to offline. How can I get my MAC to connect to it wirelessly and have it be connected without using the usb cable? The other posts online were not very helpful in solving this problem. TY