How to fill service username and password field

Hi, I did read documentation, but I still do not understand.

How can I from custom addon fill service username and password feild.

For example, I order game server, game server is created over whmcs etc etc, then, after all that, when game panel send me back username and password, how to implent it into client's service username and password feild ?

With an action hook. This one.

Thank you, I'm not sure I get all that with hooks.

Before that I did try this

$table = 'tblhosting';

$update = array('username'=>$imeuser);

$where = array('id'=>$params['pid']);

update_query($table,$update,$where);

but it's not working

I found where I was wrong, thanks.