Simply view the source of the page, copy the portion you admire and paste it into your own HTML document. Then you change the data. Some clip art pages give you permission to use the art if you link to the original page from which the art came. Some art is free for your use as you choose. Check on these things before using the art on your own page.
Most Web pages have an e-mail address at the bottom of the person who created the page.
If you have questions about how something was done, or whether or not it's acceptable to use the clip art, go ahead and e-mail the person. Most often you will get a response.