You should add 2 rows in your extconfig.conf, you MUST uncoment
[settings], in same file.
you should create table in a way described in link above, you should make changes in res_config_mysql.conf - with real username and password, to make connection to DB.
You need to restart Astrisk - and you will have users from DB.
I have no idea how to write users from DB to conf files - I don’t know any reason for this opportunity.
If you have more questions - ask me. I just solved problem we real time - and my knowledge is fresh
Please take care about version of Asterisk - I used CVS verion from 30 of July. Only new versions support real time.