Using a D is easy. It works just like a regular applicator.
Each D is made up of 3 parts: the plunger at the bottom, the applicator in the middle, and the lid on top.
First thing to do is wash your hands and unwrap your tampon. Then pull the plunger out from the bottom of the D and place your tampon inside. Make sure the string is in the lock, and hanging down towards the floor.
Move the plunger back into position, remove the lid and gently insert the tip of the applicator into your vagina. You want to aim for an upward angle of 45 degrees. Now insert the D all the way into your vagina, and push the plunger to insert the tampon.
Stop pushing just before the plunger clicks into the applicator, and gently withdraw both parts of the D from your vagina, leaving the tampon safely inside you.
And you're done! Simply rinse and wipe your D after each use and you're good to go.