Download this file and make it available to students. Model how to cut and paste text. Be prepared to give one on one assistance to some students. You may need to place your hand over their mouse hand and model how to "right click, cut, right click paste" a few times.
You might use this cut and paste practice assignment alone or with another cut and paste assignment to provide additional practice. Perhaps collect several cut and paste exercises and plan to practice over mulitple sessions to allow students to acquire proficiency and mastery.