The program has been downloaded and extracted, but I don't know if this means that it has been installed. It doesn't appear anywhere other than in the folder to which it was extracted so far as I can see.
I am using an Administrator account, and my source says that TestDisk must be run with Administrator privileges. I presume this means that it must be elevated privileges and at the command line, with any necessary switches, but with the current version I am just guessing. I am familiar with it in Windows, but don't know my way around in Ubuntu. The source gives the example, which may be out of date for current versions of both program and system, that you must be root to run TestDisk (i.e. sudo testdisk-6.12/linux/testdisk/static). All right, I have substituted the correct version number for the program, this is ubuntu not linux, and the extracted folder that includes testdisk_static is a subfolder in downloads.
Ubuntu works very well for me, but this is over my head. I would be grateful for any guidance on how to actually run the program.