From memory this is what I did:
I sold 1 Bitcoin for $15,000
So when Bitcoin fell $2,000, I was up $2,000
If it had risen to €19,000, I would have been down $4,000.
I set a limit of $25,000. In other words, if Bitcoin had risen to $25,000 I would have been closed out automatically.
I was required to put up $10,000 to cover the potential losses.
A purchase works on the same principle.
Say, you buy one Bitcoin today at $5,000.
You will have to set a limit on the fall - say a fall of $2,000.
Then you will have to put up a margin of $2,000.
If Bitcoin falls $2,000, you will lose your investment.
If it rises to $6,000, you will be up $1,000.
If you want to take more risk with your $2,000, you could buy 4 Bitcoin at $5,000 but the limit on the fall would be only $500. Once it falls $500, you would lose your entire stake.
But if it rises by $1,000, you will be up $4,000.
So when I sold Bitcoin, I put up enough margin for it to rise to $25,000 to reduce my risk.
It's a very exciting trade. But if you have any gambling tendency at all, stay well away from it.
Brendan