How do you develop chi?

Firstly by eating a balanced diet.

Tai chi or Chi gung exercises will also help. Yoga will help. Some Martial Arts may also help particularly the various forms of kung fu.

Meditation can help as well but you would need to learn how to meditate in a way which improves chi.

Being around nature (ie a walk in the park rather than a walk along a street) will help.

For women having sex will improve chi, for men it reduces it.

Also you need to reduce stress.