How can you even begin or participate in these sports?

I looked through some kind of Olympic coverage on television, I surprised many different sports competed, my question is, I understand how to participate in sports like tennis, golf, basketball, football, including badminton, table tennis, but how to even begin as a water-polo, archery, canoeing, bungee jumping, pole vault, rowing, fencing, shooting, synchronized swimming and even diving?! I mean, how even "selection" of these sports? How to get good at it and find the same competition?

Water Polo (held in Eastern Europe), Archery (is famous in Britain and the Alps), canoeing (is famous throughout the Midwest and the Mountain) Pole (well, has a point there), rowing (is famous in England), fencing (known in Western Europe), shooting (famous in the world), synchronized swimming, even (even not in force) and diving (famous). You just need to know what sports are availale in your area.