All modern bindings possess a hole for this purpose. Secure the strap to the binding. After securing it, leave it there permanently. Put your boot into the binding. Attach the loose end of the strap to the metal ring you placed on your boot.
Most straps have a clip to strap onto the ring.
Repeat the above steps with the other boot, strap and binding. Unclip the strap from the metal ring when finished skiing. Telemark skiing is a physically demanding sport that could result in serious injury. We recommend that you seek proper training and equipment before attempting this activity. Inc. How things get done.