discipline?

A
Hi everyone, this post is probably going to sound dumb but I'm not sure how to discipline my daughter at her current age. She is 20 months old and recently has become.. well, pretty terrible. Temper tantrums no matter where we are, ignoring everything I say, doing the exact opposite on purpose, etc. Up until now she has been oddly good, alwaaays listens, always nice. I know terrible 2's are coming and I know this is normal, I'm just not sure how to discipline or what is effective/appropriate for her age as she doesn't know how to voice her thoughts and feelings. Just as an example, she'll throw her plate and smash her food if she doesn't want what's given to her, or if I tell her "sit down with your cup" she'll throw the cup at me, get up and run away. It's to the point where she's misbehaving all day some days. I calmly explain why what she's doing is wrong, but she knows and that's why she's doing it lol. Any advice on how you deal with terrible 2's? I don't want her thinking she can keep up this behavior but I know it's normal so I'm at a loss.