deleting projects

If I go File > Recent Projects > (list of projects)
How do I DELETE those projects I no longer want in Scrivener?

If memory serves me correctly Recent Projects is like Recent files that other programs and the OSX sometimes list and is “remembered” in a preferences file. You might edit the preference file if you have the write tools and you know what you are doing you may edit a preference file sometimes (which I would counsel against ever doing)or delete the preferences but not only would the all recent projects be “forgotten” all the settings would go back to default for the program.

The easiest method and the one I would recommend is to use the CLEAR MENU command, but everything in the list will be lost. But after you clear the menu open the projects you want in the list and only those would be remembered.

If that makes any sense?

If you mean deleting the actual project, though, just move its .scriv file to the Trash in the Finder. When you empty the trash, it will no longer show up in Recent Projects.