Depends on where you are in the World.
For the Vineland location (closer). From Disney Springs area I would probably take Hotel Plaza Blvd to right on S. Apopka Vineland/535 under I-4, left on Vineland. Outlets are a about a mile up on the right (and now spilling over to the left). From pretty much anywhere else I would take Epcot Centre, becomes World Centre to left on I-Drive to left on Vineland. Outlet is about a block down on the left.
For the I-Drive location you'll get on I-4 East bound (closest entrance to where you are). Exit is Sand Lake (74), but from there Google maps is probably your friend. You'll head up S. Kirkman, Rt on I-Drive, and follow on to the end, or loop around behind the mall on Grand National. I-Drive can be a bit slow, the loop around might be easier.