You can designate a favorite physician or pharmacy two ways.
1) From the Physicians or Pharmacy List, just tap on the image. You should see a little red star appear. You have now added this item to your favorites. To remove it, simply tap the photo again. The star will disappear. You can also visit the pharmacy's profile and tap on the image. A red star will appear, designating the pharmacy as a favorite.
2) From the Physician's profile, tap the grey Add to Favorites button.