Hello. You did not indicate the essay to which this question refers, which makes it impossible to answer it accurately. However, I will try to help you in the best possible way.
If the author of the essay uses other people's experience to support his argument, it means that the author uses experiences that prove and show that his argument is correct, supporting and evidencing his statements. An example of this can be seen in a text that uses an argument like "slapstick comedies has lost influence with young people aged 15-20 years" and uses as a support phrase like "high school students claim that this type of entertainment has been promoting predictable experiences that do not actually promote funny situations. " With that, the author shows someone else's experience, which confirms his argument.