How to Get Your Best Friend
So, I know you are wondering, how in the world can I get a dog? Well, it's simple. Find an small area that's flat, and open up shop with the p key. Go to the placeables tab, and tap animal pens. the first thing that pops up is the doghouse for 2.5k. Tap buy and put the doghouse where you want it. After that, leave the shop and go to the doghouse, and your dog will be there.
What You Can Do with Your Dog
Well, the doghouse comes with two things with it, as well as your dog. The first is the food bowl, which you can fill up for free, and the dog will go to it and eat. The second is a tennis ball, if you pick it up, and use the throw key, the dog will go after it and bring it to you. You can make your dog follow you, stay, or go back to the doghouse. You can play with the dog with a special key, and you can pet him. I don't know if he will go into the Retriever (the Pre-Order DLC vehicle) or the trucks.