Teach a child to tell funny jokes by practicing the joke with her to help with memorization, showing her that you are listening through audio and visual actions and incorporating familiar elements to help her understand the concepts. You may also tell the jokes yourself to set an example and make her more comfortable.
Practice is one of the most important elements to teaching a child how to tell a joke because it establishes a thorough understanding of the material and makes her less likely to become nervous during the delivery. Begin by choosing a joke that is appropriate for her age and telling it to her first, so she gets to experience the humor naturally. Then, read through the joke together, and talk about what it means to help her commit it to memory. Once she knows the joke, have her practice telling it so she learns how to emphasize the correct parts.
When she tells the joke, make sure you let her know you are listening and paying attention through your facial expressions and by laughing at the appropriate moments. This also encourages her during the performance and teaches her about reading an audience. It is also important to keep the experience enjoyable and fun, rather than a chore, to make her more likely to engage in the activity and want to tell jokes in the future.