Hi Sharon, We actually spoke about this very same kind of system yesterday in Spanish class. Basically: you can upload this as a type = map. Add the URL and explain in the description that this is a live, browsable map. Important to take into account:
These systems always have shapefiles behind them. Whether or not you can download them depends on whoever runs the website. So look around to see if there is a download option. And consider writing them to ask, if you don't see it.
There are often MANY different layers. It's important that you go through the various layers and make it clear in your description which layers in the mapping site are useful to what layer in our system, so that whoever processes this has a good idea of what's there.