Not OP, but the answer is, it depends. If you're using a proper (read: slightly more expensive and probably non-acrylic) yarn ~~skein~~ hank, then yes, it needs to be wound into a ball first, then put into the bowl. The bowl keeps your ball from rolling around everywhere.

If you're using a cheaper type of center pull skein (no judgment!) then no, not really. But if you're using a center pull skein, then you don't really need the bowl. Your yarn won't roll.

I've not rewound this yarn, I'm just taking the label off and getting the end. I use the bowl to have something to put the yarn in basically and because I think it looks nice. I'm terrible for buying hobby bits because they look nice, I have so many pins and stitch markers and things.

Like another person said though, if it was one of the fancy yarns that comes in a hank (I think they're called) I'd need to wind it first so it was a ball before being able to use it.