There's no right or wrong way to tie a lariat or long necklace. Here are some ideas to get you started:
Loop within a Loop
If you used my Lariat Tutorial, you may have a long necklace with loops at either end. You could simply wrap the strand around your neck or waist or you could slip one loop through the other to secure the strand. To make the look in this photo, start by placing the center of the strand at your throat, wrap the ends behind your neck and around to the front, then slip one loop into another. Keep the sides even or go for an asymmetrical look.
Simple Overhand Knot
To get this look, grasp both strands in your hand and tie a single overhand knot. This look is also very cool when worn down the back instead of the front, with upswept hair to show the beads (and back) to their best advantage.
Tie It All Together
Another style to try is to tie one strand over another, as you would your shoelaces, except without the bow. If you like, make another wrap to form a knot. You could tie the strands close to the neck and then again further toward the ends. You could combine techniques and make a tie, then slip one loop through another. The possibilities are only limited by the length and thickness of the rope.