With a lot of patience. Once the animal tolerates you walking by the cage, changing the water bowl, feeding, and cleaning, you can try and touch it gently or even catch and hold it. If you pay attention to your animal, you will learn when it is comfortable and when not. Start by holding it for a few minutes at a time, a few times a day, and just picking it up, not holding and restraining it. The Hypothalamus is the part of the brain where most of our emotions come from.
All reptiles have one, so they likely have feelings.
The most basic emotions are fear, aggression, and pleasure. Reptiles have these feelings and express them. They avoid what they fear, attack what makes them angry, and seek out what is pleasurable. In order to like someone, the animal has to distinguish between people and clearly prefer some over others. Chelonians do tell people apart, and they prefer some people over others.