newborn sleep flat or elevated?

Marie
I have a bassinet I'm going to use for my newborn when she arrives but not sure if they are okay to sleep flat on their back? Or do they have to be elevated? Should I purchase a wedge? She also has a brand new crib but it's same question! Please help I have a 5 year old son and I don't remember how to care for a newborn lol I'm reaseraching believe me ✨