Using images, audio clips, and video footage created by others in your own work can risk infringing on the creators' rights under Canadian copyright law. While you may have rights to reuse and reproduce copyrighted works under the limited terms of fair dealing provisions - especially if your work is non-commercial and will not be published - using public domain materials can ensure that you respect the copyrights of creators.
This page lists a number of tools and databases which contain public domain materials which are free of copyright restrictions.
You should double-check the licenses of the materials you may include in your projects. In many cases, such as materials shared under Creative Commons provisions, you will still be required to attribute materials authorship to their creator, and you may be restricted from commercializing your project. It is ultimately your responsibility to ensure that your usage of copyrighted materials remains within the limits of relevant copyright laws.