Example:

Here is some text that you wish to mark-up as HTML - There are four sets of tags we need to add - The emphasis, the anchor link, the image file and the whole paragraph needs to go into a paragraph tag.

So - lets do the emphasis first:
We put a starting token in (em:) that shows the service what kind of tag it will be - and select until the end of the emphasis. Then just invoke the service (via the Command-Shift-\ shortcut or via the services menu).

Now we can do the anchor link: We put a starting token in (url:) and select until the end of the URL and invoke the service. If you put a: instead of url: then the selection will become the text of the link, rather than the URL of the link.

The Image File: Invoke the service. The "alt" tag is left empty for you to add a description.

Then we just a paragraph (p:) marker at the start, select the whole para ...and invoke the service.

And you're done.