I'm new, so I'm sorry if this is a dumb question. But is there a way to simply add a basic marker to a map without creating a long/lat coordinate table and having ArcGIS add it? All I want to do is put a marker in a fixed spot - like to say "our building is here", and then show the map around it.
Sure, you will want to add a graphics layer to your map. This doesn't create a feature or anything, it's just a graphic.
Add and modify graphics and text—Layouts | ArcGIS for Desktop
You can also just add a text element to your map as well: