Website Help: Cups

On the cup page you can see results and standings for cups, aswell as downloading levels and uploading replays.

How to play cups

If you want to participate in a cup the only thing you have to do, is to play the level of current event online in EOL. Your time will automatically be added to the results once the event deadline is over. However if you win the event it is required that you also upload your replay. You can upload replays during the event from the cup page, which is recommended even if you don't think you are gonna win, so that others can see different styles etc. If you win and haven't yet uploaded your replay, you have 24 hours after the deadline to do so.

tl:dr version: Play online, if you win upload replay.