Custom fields user's settings

[Gamempire]

Hi, in the page of user's settings, I want to add some custom fields.. i can do this by html, but after this, i want that some of new columns (that i will create in user's table of mysql).

Where i have to look for?
Where the settings are saved?

Or
What is the algorithm that creates that strange number for user settings? (like '87342103')

Thanks

[Gamempire]

nobody?