A good rule of thumb is to recall the acronym TAL, which stands for Title, Author, and License.

• Title – What is the name of the material? Provide the title of the work you are adopting. Be sure to hyperlink the title to the original sources. If a hyperlink is not available, describe where you got the work.
• Author – Who owns the material? Name the author or authors of the material in question. Sometimes, the licensor may want you to give credit to some other entity, like a company or pseudonym. In those cases, please just do what they request. Also, if the author has a webpage, please link to the author’s page.
• Licence – How can I use it? Provide the exact name of the Creative Commons license under which the work was released, and hyperlink the license name to the license deed page. You can use the acronyms instead of full name of the license.

You are obviously using the material for free thanks to the CC license, so make note of it. Don’t just say the material is Creative Commons, because that says nothing about how the material can actually be used. Remember that there are six different CC licenses; which one is the material under? Name and provide a link to it, eg. http://creativecommons.org/licenses/by/4.0/ for CC BY. The above content is from CC Wiki, CC-BY.