I am new to cake making and I was wondering, do I have to use butter cream icing under the fondant or can I use regular icing?

You can use any icing, marzipan, ganach, some peopole use a apricot preserve covering, anything that will help the fondant to adhere.

Opps......I'm sorry. I didn't welcome you to CC......I see that you are new ......Welcome....you will love it....so many fantastic members with soooooo much information, encouragement and talant.....