A cincture is a rope or cord used to tie around a robe or waist to secure it in place. Here's a basic way to tie a cincture:
Hold the ends of the cincture in both hands and wrap it around your waist, with the ends hanging down in front of you.
Cross the ends over each other in front of your body.
Bring the ends around to the back and cross them again.
Bring the ends back to the front and tie a knot in the center.
Adjust the knot to sit at your waist level and adjust the length of the ends to your desired length.
If you have excess length, you can tie a bow or tuck the ends into the cincture itself to keep them out of the way.
Smooth out any twists or knots in the cincture and adjust the folds of the robe as needed.
Note that there may be variations in how to tie a cincture depending on the specific tradition or garment being used.