No such thing as a silly question!
To check the compression: one generally uses a compression tester, which is basically a pressure gauge. You can do it without a gauge by removing the spark plug, and holding your thumb over the plug hole while cranking the engine. The engine should rather strongly push your thumb a bit away from the hole. The pressure should be around 80 pounds per square inch or more, but there won't be a lot of volume, so your thumb won't leave your hand. The engine should push your thumb a bit so the compressed air escapes "with authority". (I would ground the spark plug wire to the block to prevent electrical damage to the mag, since creating spark voltage with no place for it to go can do damage to the mag.) A lack of compression will not cause pressure to move your thumb, and has several causes. Most likely is valve leakage. Before taking the engine apart, you might try squirting a bit of oil in the plug hole. That will temporarily seal the rings and boost compression if the rings are bad. I'd to that second. In other words, thumb test your compression, then squirt the oil in and check it again. An improvement indicates leakage around the rings. That might mean worn rings, or just that the rings are dry from sitting around so long. If you notice increased compression, try starting the engine again. Perhaps the increase in compression will be enough to get it running.
Top Dead Center is a position, not an object. TDC refers to the position of the piston in the cylinder bore. When the piston is as high as it goes in the bore, and the crankshaft is centered right under it, that is TDC. If you can see the piston when looking in the spark plug hole, you can see it moving up and down while the crankshaft turns. When the piston is at the top, it is at or near TDC. Most engines have a mark on the flywheel to indicate TDC, since you can't see the crankshaft itself to see when the crank journal is directly centered under the piston.
A fairly accurate means of finding TDC if it's not marked on the flywheel is to observe the piston's travel. Turn the crank until the piston just starts to move down, and mark that point on the flywheel, next to something that is stationary. Then turn the crank the opposite way, and note when the piston starts to move down again. Mark that position. TDC will be between those two marks. This is just an approximation, but may be helpful in determining when your spark should occur.
In your case, I would expect to hear the magneto impulse coupling snap when the piston is at or very near the top of its travel.
I hope I haven't confused you further! Please feel free to ask whatever questions come to mind. That's why we're here!