Help Connecting Mac OS X Yosemite V 10.10.3 to Canon MG3120

[ehodge]

Hello! I have been using my Canon MG3120 printer for years with my Windows PC. The printer is connected to my WLAN.

I now have a Mac running OS X Yosemite, v 10.10.3. I can't for the life of me get it connected to the printer.

I can not find the install CD, so downloaded MP Navigator EX from:

http://usa.canon.com/cusa/support/consumer/printers_multifunction/pixma_mg_series/pixma_mg3120#Drive...

When I attempt to open MP Navigator after installing it, I get the error message:

I attempt to open it while having my Mac connected to the printer via USB cable.

I'm assuming I'm missing #2, the MP Driver? But I can't find a way to download it from anywhere.

Is my hunch right?