Make sure you are installing the ArcGIS app made by ESRI. You will probably need to login to the app store using your account to accept the install. It will take a minute or two to download and install depending on the speed of your connection.
You should see the Louisa Gilmer and Louisa Hotchkiss maps as available choices. Select either (both are GREAT!) and open.
The device may ask for permission to use your location. If you accept, your location will be dropped on the map (Gilmer or Hotchkiss) and you'll be able to see historic points around you.
If the map doesn't immediately show up, but you see aerial imagery, try pinching to either zoom in or out. This should activate the map. For best resolution, make sure you are set between 1:2,000 and 1:100,000.
For questions or issues, please call 540-967-5975 during museum hours, Monday-Friday 10 am- 4 pm.