Quick PHP job

I have developed a registration and login page using dreamwever CS3. I have developed an update form using CS3 so the user can update their info in the data base table. All info is held in a table [mysql]. Each user has their own row in the table. It all works except for one thing that I need quick help with. When a user registers and then logs in I need them to see only their info in the update form. I do not know how to code my PHP for this. It always goes to the first row in the table or first user. I need the login session [already setup] to some how dynamically pull up the relative users info or row in the table based on their user ID. each user has one row with a unique ID. I think it is an if/else statement or switch using the session? I need this done quickly, Thanks