The price rises to $50,000, at which point you close your position.
Suppose the price of Bitcoin is $45,000. You’re bullish – so, you take a long position on 2 coins. The price rises to $50,000, at which point you close your position. Since your prediction was correct, you’d make a profit. The price went up by $5,000 – for 2 coins, that’s a profit of $10,000.