How to write a characterization
A characterization is a description and interpretation of all the features that make up a personality, his/her situation in a story, the relationship with the other characters and his/her development within the story.
Before you begin with your characterization, you may want to collect the relevant information in the text at hand. You can mark them, make use of a table, a mind map, notes, etc.
Then you start with an introduction giving some brief information about author, primary text, and which character you are going to analyze. It may be useful in some cases to add information on the constellation of characters in the situation given.