....the power wire for an electric coolant temp gauge, where in the fuse box I mean? This is just for power to the gauge, not for the lights.
And how do you attach it to the terminal? Can I just splice into the hot wire for my aftermarket alarm?

 

there should be an acc (accessory) spot in your fuse box tap into that. I used a forked end wire terminal and soldered on there. make sure you put an inline fuse in as well.