Depending on which database you're using, it will be different. However what's nice is the SQL statement will always be the same. Are you having problems connecting to the Database and then running queries? If not just enter a query such as
querystring = "UPDATE tblUsers SET PASSWORD = 'bettersecret' WHERE USERNAME = 'JRGrant';"
then connect and run querystring. The database you select, and column name will be vender specific. You can easily look up how to update that specific DB at the venders website. But the query is roughly the same idea.