Hi, I am A. Stevens here to help with your question!
There's a couple of things to do here.
1.) Have you set up the printer to your WIFI network at this time yet?
Could you tell me where you encounter the issue?
You should be able to connect your printer to your WIFI using the control panel on the printer.
Then you are correct that your mac is too old.
The latest version is OSX 10.9
and so the printer setup is incompatible with 10.5
There may be one thing to do, we can try to find an archived version of the driver for older OSX.
But the printer is fairly new so they may have never created a driver for 10.5
Or another option would be to try to use a generic print driver.
But I haven't seen much success with that in the past.
Any reason why you don't want to upgrade to 10.9?