yes, of course. The configuration file is in /usr/local/etc/freetds.conf (depends by version anyway). It's recommended to add an entry for your database connection, such this

[MY_DB_NAME]
host = 12.34.56.78
port = 1433
tds version = 7.0
database = my_database
user = my_user
password = my_password
[download]

You can configure all of this options or less. In MY_DB_NAME you create an alias for the configuration; in "host" you enter the db's ip and in "port" the used port (usually 1433 for MS SQL). In "database", if you need, you enter the start database, and you can also add values for "user" and "password". I've seen in various forums that the best working tds's version for MS SQL is 7.0, so it's recommended add the "tds version" value with "7.0" such in the example. After, you can recall this connection configuration simply by the alias, like this /usr/local/freetds/bin/tsql -S MY_DB_NAME. If you're missing the "user" and "password" values nevermind, you can always launch tsql in this way /usr/local/freetds/bin/tsql -S MY_DB_NAME -U my_user, and so on. I hope it's helpful.