Women at the department store snickered and glared at the narrator as she walked by how does this detail support the text main idea

Although your question does not give very much context regarding what was happening in that specific piece of literature,

The idea that nearby women were making fun of/snickering at the protagonist in the text suggests that she is not well-liked. It also could suggest that the women who were snickering are the antagonists / are mean to her.