bonus videos that are already rendered (mp4) can be added to a project by clicking Videos in the left menu then click the folder icon at the top near video path to browse and find the video you want to add.

bonus content like images, sounds can be added to the library in the app by clicking Images or Sounds in left menu > then Add (you must start a new project first for left menu to work) > then Upload button lower left.  browse your computer for content and click to upload.  it will be added to the library.  note: you must unzip first--you cannot upload a zipped file with bunch of content, only the files themselves, but you can upload multiple files at once by holding CTRL and selecting all the files you want then click Ok.