How can I use a script to find an object with a certain tag and instantiate a prefab at its position?

I'm making a minimap, and it's basically a camera in the sky looking down at the ground. The minimap blips are planes in the sky just below the camera's position.

I know this isn't the best way to do a minimap, but it's the easiest way I could think of, and I'm lazy.

I haven't coded at all in two months, since I was on a trip to Vietnam, and I'm totally blanking. Can I have some pointers in the right direction?