How do I erase and restore

Robert, when you say 'an app' - I assume you mean an installed program / application with any associated files.

Further assuming that this has been installed to the default C:\Program Files or (x86) version of the same location, then you are looking at needing to do a restore of a disk backup containing your OS partition from prior to when that app was installed.

Please see KB 19296: Acronis products cannot be used to transfer applications to different system or upgrade OS

Most installed applications have data installed in multiple different places, including the system registry hives, user AppData folders as well as the program folders.

One approach that you can try, assuming that you are confident in working with both Explorer and the Windows registry editor is as follows:

1. IMPORTANT: Make a current Backup of your OS Drive before doing anything!
    
2. Open Windows Task Manager and check that the problem app does not show in the list of Startup apps that will be automatically started with Windows.
    
3. While still in Task Manager, look in the Details and Services pages for any reference to the problem app and end any associated processes / stop associated services (if identified). 
   Note: if you see any Services, then open the main Services.msc control panel, find the service and change the start option to Disabled.
    
4. Look in the following folders for any reference to the problem app.
   Note: You need to enable 'Show hidden files, folders and drives' in the Explorer options to see some of the below:
   C:\Program Files
   C:\Program Files\Common Files
   C:\Program Files (x86)
   C:\Program Files (x86)\Common Files
   C:\ProgramData
   C:\Users\[Your-Account-Name]\AppData (in particular in Local & Roaming folders)
    
5. Delete or Rename the parent folder(s) for any related items found in step 4.
   Note: if any items cannot be deleted or renamed, then check for that item (name) again in steps 2 & 3.  If not found, then try restarting Windows.
    
6. Use a tool such as CCleaner to remove any associated Registry entries for any items deleted in step 5.  You can also use CCleaner to check step 2. for any startup entries! (Open CCleaner then click on Tools then Startup).
    
7. Open the Windows Registry editor (regedit) and do a search for the app by name or by the program path where any executables were found in step 4.
   If you find items, then right-click on the item and Export the key from the registry as a safeguard against any mistakes before deleting the item.
   Note: this step may not be needed if step 6. is able to clean up successfully.

I would suggest also looking at IObit Uninstaller and seeing if this can remove the unwanted app for you - this would do most of the above for you automatically.