Expect confusion and mistakes in the first few days, even in a trained dog. It is vital to use a crate and/or a confinement area so as to not allow opportunities for accidents in the first week or two - this also helps chew-training efforts.
Set your dog up to succeed. If using a crate (highly recommended) it should be just large enough for dog to turn around in and stretch out. If using a confinement area, confine to one uncarpeted room with petproof gates. You can always relax the regime later, but it is very tough to start relaxed and then try to tighten up if there's a problem.
Provide extra opportunities to eliminate outside: First thing in the morning, after eating, every 2 - 3 hours, and last thing before bed.
If your dog doesn't eliminate on any particular outing, try again an hour later. Accompany your dog to eliminate - go with him rather than sending him so that you know whether he's gone or not. You can reward at the right instant - give praise and small food treat as he finishes. Go to the same spot to make it easier, or at least the same kind of surface. Praise and reward all outdoor elimination for the first few days - later you can slack off (it's okay to continue praising.)