Does anyone know how to use these things?

Once you fire the missle, you guide it like you would fly. Use your mouse/joystick/KB to guide it to it's target. It's sometimes the only way to get to a switch behind a grate.

As it turns out, i did not have the guided missiles in the secondary autoselect rotation so they never came up as a useable weapon. your reply got me thinking about those menus and led me to where you can set the autoselect order. for years i picked these things up and never even fired one. i have to say these things are sweet. thanks for the point in the right direction.

How do you get skill points in the Descent 1 game?

Skill points are in the Ace or Insane skill levels