How to gain your dog's trust
-BE PATIENT. Your dog has no reason to trust you, so you will need to be patient and let the dog take its time.
-Create a schedule. Make specific time to feed, go outside, play, relax and sleep - and STICK TO IT. You want your dog to learn to trust the world and that it can depend on the world to function in a reliable and non threatening way.
-Try to hand feed. This teaches your dog that you are the source of good things in their life. Start feeding time off with offering food first in your hand, don't expect them to do it at first, but eventually your dog will trust you enough to eat directly out of your hand.
...Or use treats. Sit on the floor, at your dogs level, and lay treats all around you. Over time (which could be days or weeks) the dog will eventually get closer to you to get the treats. Once they get closer to you, very slowly move your hand closer to the treat. This establishes that you are safe to eat a treat around. Eventually start moving the treats closer to you until your dog gets to the point that it will take a treat directly out of your hand.
-Show your dog you mean no harm. Simply sit near them and read them a book or just talk to them in a soothing tone. Don't corner or force your dog to be close to you, just offer yourself and show you mean no harm.