DB security

Hey, new here. I recently got a summer job doing VB programming. Unfortunetly, my VB is fairly limited. So when i was asked to do a login password for an sql database, life became dificult. So, was wondering, is the any tutorials out there for this??? I know theres one coming out soon. But i need something quick. Coming up with screens is no problem, nor is basic code. Basically, there are 4 user levels to this and users are stored in an sql database. So, there ya have it. Replys much appreciated.