Hi Chris. A puppy can be in the grass in your own yard if you have one. If you live in a shared space like a condo or apartment, that can be trickier. You can get a patch of real grass (put sod in a tray or buy a pre-made potty station) and put it in a garage or deck to help your puppy get used to going potty on grass. Also keep in mind that 20 weeks is when vaccines are considered “finished” (fully administered and effective) but puppies start building immunity from birth when they start nursing on the mother. If your puppy has had at least one round of vaccines, finding a spot around your building where you don’t ever see dogs go may be low risk. Talk to your vet about the specific risks if you want more information and tips about that.