He harassed her by following her to work everyday. The Ewell's also whispered obscenities at her and only stopping when Deas (Robinson's boss) threatened to get him arrested.
Jem goes with Atticus to tell Tom Robinson is dead
Bob Ewell is involved in accusing Tom Robinson of assaulting his daughter Mayella, attacking Atticus Finch after the trial, and threatening to seek revenge on Atticus and his family following the trial.
Helen Robinson falls down because she is overwhelmed with emotion upon seeing Atticus Finch arrive at her house to deliver news of her husband's death. She collapses from the shock and grief of the situation.
Bob Ewell targets anyone that insulted him at the trial. This includes Atticus Finch, as the top of his "hit list." His two other notable targets were Judge Taylor and Helen Robinson, Tom's wife. He failed in hurting either, and when he tried going after Atticus' children, he died at the hand of Boo Radley.
Although he won the court case, Atticus obviously proved Tom innocent, and he completely sided with Tom anyways. Bob Ewell is angry that Atticus sided with Tom, and he tries to take revenge by killing Atticus's children, scout and jem. He does not succeed, thankfully!
Mr. Link Deas learns Helen is walking out of her way to work because Bob Ewell "chunked at her". Mr. Deas walks Helen home that day and shouts into the Ewell house that if Helen has any more trouble he will have Bob Ewell arrested.
Helen was afraid to pass by the Ewell's house
Atticus sits in front of the Robinson house like a guardian when he is waiting for Helen, showing his support and protection for her as she walks home from work.
Atticus asks Mr. Tate if he sent for a doctor when he arrived at the Ewell house, to which Mr. Tate replies 'No'. Atticus then asks Mr. Ewell why he didn't call a doctor, to which Mr. Ewell hesitates and does not provide a clear answer, indicating their lack of concern for Mayella's condition.
Scout found out what happened at Tom Robinson's house by following Atticus to the jail where a group of men were attempting to harm Tom. She, Jem, and Dill arrived just in time to witness Atticus diffusing the situation with his calm demeanor and determination.
jem and dill
In the last part of the story, Mr. Ewell follows Jem and Scout home when Scout is wearing a Halloween costume. Ewell attacks Jem, but Ewell intends to hurt Scout as payback to Atticus. When Ewell throws Jem about, Jem breaks his arm-- but that is not known until Bo carries Jem to the house and Atticus calls a doctor.