please help, how to preparing for the second ER nurse interview

Congratulations on your interview and good luck!!!!

Congratulations on your interview.

RELAX.

You don't need to study for a job interview (except for some flight services, but that's whole different ball of wax). THEY KNOW you're a new grad. THEY KNOW this is your first RN job. They aren't expecting you to display encyclopedic knowledge of all possible patient presentations and treatments. There many not even be any mention of your knowledge base. All they're counting on is that you learned the base-line stuff taught in school.

Just be clear about your desire, your willingness to learn, to work hard, to help out. Don't try hard to impress them; just be yourself. If they don't like that, then you don't want to work for them. You want to work for someone who will take you as you are, new grad RN, and teach you and help you grow into the job.