(close to cardboard you go). once gone through, make a knot you will tighten when pulling the yarn.
now take the tassel of the cardboard and make few more knots like this, pushing through the middle of the tassel, making knot and pulling.
once done, you will see your tassel becoming firm at the end where you have sewed. now try to push the needle through the yarn on top of the tassel (one you sewed while making knots). make three-four knots on top of it.
your tassel is finished and ready to be sewed on head now.
if you will find it difficult to follow (because i am very bad describing and specially 