Hi,
No one is actually winning $. There are 3 ways to win here.
1. Ready-go style where you pay entry and higher you place wins you higher % of the pot.
2. Premium tournaments where you can win gift cards to amazon.com and other premier retailers.
3. Premium tourneys where you can win from putter, handbag, to major vacations.
Now, when someone wins those, the value of each prize is added via earnings in dollars, Therefore you see people who won $15k, while $ wise they won 0 but credits + prize value is $15k.
You can enter them at any time I believe. As long as your country is allowed and you meet other specific tournament requirements (which vary from 1 to another).
This is a brief breakdown, but I think it should give you an idea.
-wgticon