They may include screen shots from notation software. They may be created using a digital camera. Regardless of how the graphics are created, eventually they are saved to disk in an appropriate file format. The two most common graphic formats on the internet are gif and jpg. The gif or jpg file should be copied to the same folder as the index page.
Graphics files are visible in the web page after they are dragged into the composer window.
Adding sounds to a web page. Again, sounds come from a number of sources. They may be downloaded from the internet. They may be created using software for notation, sequencing, or recording digital audio. They may be extracted from CDs.