That is actually an SAE connector, not USB. It looks like a USB attachment comes with it, but that is only one of many attachments you will be able to use.
The "exact" way to hook it up is like Bobdirt says, except you always disconnect your black (negative) wire first, and then hook up your red wire (positive) and then black.
It's water under the bridge now, but I would install an SAE connector with a 10A fuse instead of the 3A one you purchased. I don't know what those wires can support fuse wise, but with only 3A, you are kind of limited with what you can do.
If charging your phone is what you're after, you can plug a USB into your cigarette lighter on the dash.