You can configure Database hostname and port from configuration file of odoo. So it's trivial to add different database then localhost, here is part of config file (default record) you'll need to change:

db_host = False
db_port = False
db_user = odoo
db_password = False

Please make sure that at the database server all access configurations are set properly, to accept connection from your odoo server. that's it.

Thanks very much :)