clip the halves together and tie the tie AROUND YOUR LEG. I won't go into how to tie a bow tie here. You can find instructions all over the web and I've included a link to one example here. It is very easy to do around your leg. Remember, a hand tied tie is NOT supposed to look perfect. Once you have something you like, carefully unhook the finished tie.
Hint, adjust loop to make the tie as big as possible. This will give you more material to work with.