If this is something you would be interested in it is best to start this training young.
Siberians are a naturally curious breed and enjoy the outdoors. Using a harness allows them to explore safely.
I recommended getting them used to their harness within the house and reward them with a treat such as a lik-e-lik to create a positive reinforcement with the harness. Then allow them to explore in the garden at their own pace, it’s okay to encourage them but not to push them too much. Once they have gained confidence you can try going for walks.