Steve Auxley shows how to add tippet to a fly fishing line. He mentions here that you do not add tippet to fishing line, you add it to the leaders. So lets see how you do it. You hold the leader in one hand and about two feet of tippet in another hand. Now you are going to tie a knot between these two. It is called as a "improved surgeons knot". You just take six inches of the leader and six inches of the tippet and put them together. Then you make a big loop. Next you put the tag end of the leader and the entire tippet through the loop, tighten it a little and then repeat the same procedure. Before putting and tightening the knot, moist it a little to reduce the friction. And that is it! This is how you add tippet to a leader (fly fishing line).