3. Find an online betting exchange
An online betting exchange is just like an online bookmaker, except they are a lot rarer and at an exchange you have the ability to lay a bet. When you lay a bet you are betting against that event happening. You have the ability to win other punters' money on the exchange (as you are taking the place of the bookmaker; accepting money for bets and changing odds etc). So if you were to lay Chelsea to win the league at odds of 2 with a stake of £10, you are basically gambling that Chelsea will not win the league. If Chelsea won the league you would have to pay out £20 (the £10 stake and then their £10 winnings) so you have made a loss of £10. However if Chelsea don't win the league you will get to keep the £10 that someone has bet with you.

A screenshot of the cash deposit screen at online exchange Betfair