He's really, really adorable.
I'm a first time puppy/dog owner myself, and I would say the first thing you should do is take him to a vet for an initial checkup, and since he's so young the vet will probably put him on a schedule for all the vaccinations he needs.
I would ask him or her when it's okay to socialize with other dogs, and when he has a clean bill of health just love him like crazy.
Now is also a good time to start some basic training, housebreaking, etc, but again, with Yorkie blood and being so young I wouldn't expect too much right now.
I'm sure others can add more, but keep us posted and definitely post more photos.