Yes, you would want to have a salesman id column in your clients table. This id will relate to your salesperson as a foreign key but nothing extra needs to be done in the db to make this association. You will just be using the id for the currently logged in salesperson to insert into this column when a new client is added.
If you have Security Assist in place for the login of the salesperson then you can create the client insert page with DataAssist. When you are configuring the insert server behavior you will just select the session variable that holds the id of the logged in salesperson for the value of this salesperson column in the clients table.