Hmm...an easier way to find a theme of the story would be either scheming through the story looking for clues or facts or read it.
I hope this answer helps.
A lot of advice is available for people who want to form new habits for themselves.
Explanation:
Since the antecedent is plural, then the pronoun must be plural. People wishing to form new habits ought to be given a series of advice on how to go about it.
