Hi delphide brain,
When you are logged in use this link http://www.freesound.org/forum/profile.php?mode=editprofile
If that doesn't work follow these steps---
In the lefthand column under "Control panel" press "Your data"
On your "User" page press "Forum details"
On your "Forum details" page, in the top row press "Profile"
Here you can change anything you want.