How do I use my Turbotax deluxe product I bought for my tax retn, to do my sisters return too?TTAX Cust Svc told me before I bought it I could do more than 1 return?

I started a free return. It ended up charging me $135.00 for Federal and State. I only paid because I was told I could use this program for my sisters also. Now I can find no way to start a new return for another person.