Distributor can only be plugged in one way.
Disconnect wire harness and distributor cap.
Remove holding bolts.
Note direction of rotor for easier installation.
Pull distributor out.
To install, turn rotor to original position and push distributor in, twisting the rotor slightly to enable the keys to be slotted in correctly.
Install holding bolts, try to tighten the bolts as close to opriginal position as possible.
Reinstall and start engine. Use timing light to check ignition timing and adjust as necessary.