I want to make red velvet cupcakes from duncan hines red velvet cake mix. what other ingredients do i need?

Most cake mixes take 3 eggs, that would be rather difficult to divide by 4. I suggest you make the entire batter, bake 6 cupcakes out of it, then put the rest of the batter into a cake pan and bake it. If you don't want to eat the cake right now simply wrap it well in Saran Wrap and place it in the freezer. Cakes freeze VERY well if wrapped tight. Since you would have less batter than normal don't use the 13X9 pan, use a smaller one instead. Just the next size down.