Hi Im Dave,
. The easiest thing to do, is to take off the distributor cap (don't disconnect the plug wires) and look at the metal contacts on the inside. If they are covered with corrosion (flaky white stuff), then take a screwdriver and scrape it off. Note that if it is very corroded, it may mean the contacts are too worn and need replacing. If your cap needs replacing, your wires probably do too. But you can test a few other things for free, before you spend the $20-$30 for a new cap, rotor, and set of wires.
One of the most common causes of ignition problems on the Fiero is the ignition module. Many parts stores will test it for free, or you can buy a $30 tester that will do it for you.
If you don't have anywhere handy that will test it for free, disconnect the wire leading from the coil, at the distributor. Set it so that it is next to something metal, like one of the nuts on top of the strut tower. Have someone crank the car, while you watch (not too closely!). You should see an arc of electricity from the wire to the metal. If not, your coil is not firing. This means either your coil is bad, or your ignition module is bad.
If it did arc, then check the individual spark plug wires in the same way. You should see a nice blue arc every time. If you get a good spark on some wires, and not on others, replace the wires. Then re-test. If you get the same results, replace the distributor cap and rotor.
If the hold-down bolt on the distributor is missing or if you have removed the distributor, it may have become turned enough so that the timing is too far off to start the car. You will have to set the timing to fix it. If the distributor was removed, you may have to re-time the engine.