take the cap off the old distributor - make note of where the timing is. take of spark plug wires, and the wire harness going to the dist. unbolt it and pull it out, straight up.
put the new one in, in the same position the old one was in. make sure the timing is the same place as the old one was when you took it out. if not, pull it up and turn the top a little, then put it back down in. bolt it down tight, and wire it back up.
it is important you get the timing correct, and you put the plug wires back in the right place.