I assume you mean three ply. I believe it is pretty much the same as two ply. I just twist as with two ply and alternate the third ply just the same as with two...if that makes sense. Twist one way and cross the plies over the other way.
Someone will probably show up with a clearer explanation or point you to website. I will look at my bookmarks. If I have something I will get back.
Good luck!
Harold