Go to the Choose Questions page by clicking on the word Play in the menu bar at the top of the screen.
After you have searched and found the question set or word list that you would like to make a copy of, click on the three dots in the bottom right corner of the question set panel and then click on the word Copy.
This will make a copy of the questions and you will then be able to edit them. You can find the copy on your My Questions page by clicking on My Questions in the menu bar at the top of the screen.
The title of the question set will be the same as the one you copied, only the text - Copy will be added to the end of the title. You can then click the word Edit to modify the questions how you see fit.