Visit the hobo area and get their help, then return to Arlene! You'll need to sleep a few times to move the clock forward
Im sorry for another question but what do i do after i steal the keys? I cant attack them alone and i dont know who i need to be with me.
Basically any NPC with a portrait can help you, if you have a good enough relationship with them. Except for Arlene. Hers you need to do something special to get her help (and is required if you want to avoid ending the game after rescuing Cassie!)