You make up a number and multiply it by a number you've plucked from your ass. You then add 5 zeros to it - when no one is looking, obviously - and then start typing in threads just like this one. It's easy!
For seasoned pros it's different. You want to suggest that you're fabulously wealthy but without needing any of that awkward stuff like credibility or likeliness of not being a jobless bum.
"I banked 5 mill yesterday, it was a slow day (here, I'm showing meekness and am open, vulnerable).
When the markets open tomorrow I will destroy them with the strength of a PUMA! (here, I am being manly, also rich, strong animal overtones which is always worth while)"
Watch and learn.