Going on a funeral, how should I behave?

Hey everyone, my uncle has recently died and this will be my first time going into the funeral. How should I dress and behave? Should I greet my aunt and give condolences, or just attend funeral and not bother her? Should I bring something to give to her as my condolences? What do I say when I approach her? I’m completely confused and I don’t want to appear cold or weird there. Any help?