Find a on the internet a picture of your choice and copy the url to it.
Overwrite the code line in the given sourcecode
Execute your script by having it run.
Save your solution accordingly.
Download another picture of your choice.
Create in your W3 workingspace a directory media and save the downloaded picture there
overwrite the url in the app to display your new local picture
Execute your script by having it run.
Save your solution accordingly. Therefore you might need a W3-School-account.