You can upload your data to use inside the website in the library and use the link to reference it inside components, stories or within the text editor.
You can upload any type of file you like (video, pdf, xls, image...)
To visit the library, click on to the following section on the left side bar
You can click on "upload" to upload your files.
Pixabay photo library
If you like to search photos on the fly and download them to your library or use them directly into your website, you need to signup to pixabay and add your public API Key, you can find details in pixabay docs
Now you will be able to search millions of photos and use them directly without leaving the editor.