The first step is to remove the drive chain from the conveyor drive motor. This will allow you to move the belt by hand to insure it is adjusted straight and also help get access to the set screws in the sprockets.
Next, align the drive sprockets and blank sprockets on the unload end to the outside and inside edges of the conveyor belt. Loosen the set screws holding the blank sprockets in place and slide them to the very edge of the wire belt. Then tighten the set screws to hold them in place. Now do the same with the two outside drive sprockets. These should be slid to the very inside edge of the outermost space of the wire belt. Once adjusted, tighten the set screws. This should hold the belt in place and not allow it to walk.
Once the belt and sprockets have been aligned, you can reinstall the drive chain. You should now be all set.