Copyright Protected
Some graphics are copyright protected and cannot be used without the author’s permission and / or paying a usage fee. Other graphics are in “public domain” and therefore not subject to copyright. Here is a flowchart that will help you determine if a graph is free to use with no limitations.
https://visme.co/blog/how-do-you-know-if-something-is-in-the-public-domain/
Give Attribution
If you are using a graph that you found in an e-book, a library database, or elsewhere, be sure and list the source underneath the image. The APA citation below represents a graph retrieved from the library’s Statista database.
To find examples of MLA, Chicago, citation styles, use the Purdue University’s Online Writing Lab (OWL) website, https://owl.purdue.edu/.
Correct Citation Format for Chart Shown Above (APA Style)
Internet World Stats. (n.d.). Countries with the highest number of internet users as of December 2017 (in millions). In Statista - The Statistics Portal. Retrieved May 28, 2019, from https://www.statista.com/statistics/262966/number-of-internet-users-in-selected-countries/.