1: Put the ignition coil on the bench.
2: Have a source of 12 volts available, such as a car battery. A wall-wart probably won't cut it unless it's rated for well over 1000ma (1A), and more is better here.
3: Insert a spark plug into the coil.
4: Take a length of wire, strip one end several inches, and wrap that end around the threaded portion of the spark plug, securing it with tape, zip-tie, etc. Connect the other end of the wire to the GND or (-) side of the 12v power supply.
5: Connect the (+) and (-) terminals of the coil to the 12v power supply.
6a: When I've done this, I have had a second power supply available to supply 5v to the trigger input. This one can be a small wall-wart, or one of those battery holders that puts 3 AA batteries in series.
i: If you have this available, connect the (-) or GND side of the 5v supply to that of the 12v supply.
ii: Tap the (+) wire of the 5v supply to the trigger pin of the coil very briefly, and the plug should spark.
6b: If you do not have a 5v supply available, you can probably get away with triggering via 12v:
i: Install a 1k resistor in series with a piece of wire.
ii: Connect one end to the (+) terminal of the 12v supply, and tap the other to the COP's trigger terminal.
iii: I don't guarantee that this will work / not destroy your coil.