Prepare for an interview? Take copies of any diplomas, work history, etc.
Get a haircut so you look clean (no particular style). Wear regular work dress clothes, nothing nautical. Hide any tattoos, remove piercings. Speak clearly and in full sentences, don't make too many jokes.
Let them know you are available and able to work (not responsible for any kids, sick parents, etc).
Talk about work history, things you have accomplished, etc.
I don't know why it would take 5 hours unless there is waiting time involved, and maybe being escalated to meeting new people as you pass one interview and move to the next level.