The ability to add your own images to questions and word lists is a premium feature of the Games Subscription. If you do not have a subscription, you can only choose images from the provided image gallery. To learn more about or purchase a subscription, please visit the Games Subscription page.
In the Word List editor and the Multiple Choice questions editor you can access the Image Gallery and then upload your own images to your questions. To learn how to get to the Image Gallery, read the tutorials Creating Word Lists or Creating Multiple Choice Question Sets.
To upload an image from your computer into a question or word list, click on Add Image in the top bar of the image gallery and then choose an image from your computer.