i have been told not to use a plain box mix to make a cake if i am going to
use bc frosting. Can anyone give me the receipe I should use to add to my box mix. Thank you

I have heard that response if you are going to use fondant, because sometimes the weight of the fondant can squish the cake...but I've never heard of that for buttercream.
There are alot of great recipes on here for doctored box mixes as well as great scratch recipes, click on the recipe tab.
I use a doctored box mix, but when I first started i used a plain box mix with out any problems.

Hi and Welcome to CC, ldydi.

Everything you need to know to make, decorate and assemble tiered/stacked/layer cakes:

http://www.cakecentral.com/cake-decorating-ftopict-605188.html

The above superthread has popular CC recipes for crusting American buttercreams, several types of fondant and doctored cake mix (WASC and other flavor variations) and so much more!

HTH