I have the same MB as you, or at least one version. Remember that each USB header on the MB is good for two USB ports.
So, the WiFi GO card goes in the area of your I/O ports, just above the VGA and HDMI outputs and below the USB ports. You MUST put this on before putting the motherboard in the case, as you need access to the rear of the MB. Refer to the WiFi GO manual that came with the MB.
As far as the USB ports, the ones along the bottom of the MB - on the side where you plug your case power button and LEDs in - are the 2.0 slots. The USB 3.0 plug is right next to the 20-pin power connector, just beneath the DIMM slots.
BTW I'm looking at pages 2-2 and 2-3 in the P8Z77-V Users Guide for this info. There's a lot of good stuff in there - the only thing that won't be covered is the WiFiGo card, which like I said should have come with its own instructions in the small package it was sealed in.
As far as the other USB connectors, if your case has USB 2.0 ports as well, it doesn't matter which of the four spaces you use - they're all identical. And yes, there are four - three to one side of the BIOS flashback button and one to the other side.
Hope that helps!