I was taught to pipe a shell with a star tip, bake off then cut in half horizontally, then cut the top in half vertically. pipe the swan heads like an S and make the head a little bit bigger and form the nose to come to a point (use a thin smooth tip). to assemble: fill the bottom shell with pastry cream or whipped chantilly cream(sweetened vanilla whipped cream) and place the S head up in the cream towards the thick part of the shell. place the wings on each side and thats it. you can pipe some more cream on it to clean it up a little bit.
Here are some pics i found to help you see the form a little?Pic 1Pic 2
I hope my directions make sense, good luck,