That's the question...
If so, how? I don't see a designation for them anywhere.
Depends on what editor you are using. Assuming Potlatch 2, they are there under the section for Transport, called "Car parking" (you might need to click "Show all").
Or you can switch to advanced mode, then add the tag "amenity=parking".
Note that where possible, it is a good idea to map parking as an area, not just a node. As this shows how big it is, and the area it covers.
Got it - thanks
It also might be a good idea to tag your parking with a name ,particularly if you want to search for a parking lot.