One of two methods. The first is hit or miss and may not be much help. That is to realize there are no limits to what you can imagine, and the dream is your imagination made real. Two schools of though exist on dream control. The first is that you do not need to practice a certain skill, instead you just build confidence and can do anything after you get yourself convinced. I have no problem with that, but have not found it very helpful, and it sounds like hard to apply advice.
The second method is to develop powers through training. The training can take place in LDs and in waking life. In LDs start with small steps that seem to build towards your goal. Maybe you should start with simply finding a dog or wolf in your dream. That is basic summoming. Then you may work on having one appear in front of you, advanced summoning. You could try looking at your hands and just try to see long claws on your fingers. Get the idea? Training your mind to handle bigger powers. Training while awake is a long process of developing mental control and visualization skills. I teach useful skills in a DVA class, here is the link, Dream Yoga (Sivason) The material is very challenging and mind expanding, and will likely take the best students a year to get down, and decades to master, but it leads to extreamly good dream control powers, of which, advanced transformation is one of them.