What else do I need to put a Flowmaster muffler on my Scion tC?

The boyfriend bought me a Flowmaster muffler for Christmas. I don't know what series it is or anything like that. He wants me to come over so he can take my car and get it welded on.... and he wants to pay for it. I say no, I want to pay to get it put on. He just has the muffler, no pipes or anything like that... do I need anything else? or do you have any advice for me.... anything will help.