It's important when you look for material to put in your project that you consider the copyright status of that work. Even if something is freely shared on the internet, it doesn't mean that content can be copied and shared freely without violating copyright. There are two kinds of works you should focus on in your searching that allow for straightforward reuse:

• Materials that have a Creative Commons license on them, meaning they have been shared openly by the author
• Materials in the public domain (most materials published before 1923)

See the Understanding Copyright tab to learn more about Creative Commons and public domain.