Use of both items is pretty simple, which is why I like them being simple minded.
To use the light, simply connect the alligator clip to a good ground, and touch a terminal, fuse, etc in question. Example, lights not working: First touch test lead to hot side of battery to make sure your ground clip is making a good connection. Then with light switch on touch to screw on back of light housing. Light comes on, problem is inside head light. No test light, problem is toward light switch. Next move to light switch and touch to headlight wire terminal there. Light, probably broken wire between there and head light. No light, touch to lug the terminal attaches to. if light, clean connection, no light move to fuse. Touch both ends of fuse. if light on one end, replace fuse and clean holder clips. If light at both ends test again on clip instead of fuse. light on one end and not other, clean clips. Light on both ends, switch is probably bad. No light at either end of fuse, check wiring coming to light switch.
To check for power to ignition, touch to switch side of coil (switch on), which is normally the - side on 6 volts, and + side on 12 volts. No light, move toward ignition switch (checking both ends of dropping resister if you have one), keep moving toward battery until light comes on. When it lights you have passed the problem, whether it is broken wire, bad switch, etc.. If light on hot terminal, move to distributor side of coil. light should go on and off 2 times per revolution when cranking engine, preferably by hand so it is easier to see. Light should be on when points open, and off when points close. Light off all the time, disconnect wire to distributor. If light comes on them, you have a short in distributor, maybe condenser, or points stuck shut, or rarely a shorted insulator where wire enters distributor. If light does not come on, coil is bad. If light is on all the time, check for broken wire between coil and distributor, points burned or dirty so they do not make contact, etc.
For the spark tester, connect it to the tower on distributor coil or mag coil using an extra spark plug wire. Set gap of tester between 1/4 and 3/8 inch. Turn ignition on and crank tractor. Should get spark 2 times per revolution for 4 cylinder engines. if no spark, trouble shoot coil. points, wiring, etc. If proper spark, reconnect coil and connect tester to distributor cap either using the spare wire, or plug one of the spark plug wires into the tester. You should see a spark every other round. If no spark, check cap, rotor, and spark plug wires. If spark, check spark plug. If you get a spark there, check carb. and fuel supply.
