how does the writer potray the social/historical context of the novel usin the theme,setting and characterisation?

Purple Hibiscus takes place in Enugu, a city in post-colonial Nigeria. There are a few themes to consider. Your question on character is also broad. I'm hooking you up with two GradeSaver links that should help,

http://www.gradesaver.com/purple-hibiscus/study-guide/character-list/

http://www.gradesaver.com/purple-hibiscus/study-guide/major-themes/